Imaging the breast has evolved from mammography alone to mammography with adjunctive modalities that primarily include ultrasound and magnetic resonance imaging (MRI). Until recent years, ultrasound and MRI have functioned as problem-solving tools and have been used to help to diagnose a mammographically and/or clinically detected abnormality. As these modalities have improved technologically and vast clinical experience has been acquired, so have their roles expanded from diagnostic tools to potential screening tools as well.
Ultrasound has many uses that relate to the evaluation of breast masses. Sonographic guidance is used frequently for the direction of percutaneous breast biopsies. MRI was initially used for the evaluation of implants, but it now has several roles that relate to the evaluation of carcinomas. With a dedicated breast coil and contrast enhancement, MRI has been of great value in identifying the extent of carcinoma and in helping to better plan patient management.
In this chapter, the discussion will not focus on the technical aspects of ultrasound or MRI. Instead, the focus will be on the roles of these ancillary modalities in complimenting mammography and the information that can be provided to enhance the clinical knowledge about the patient.
The Role of Breast Ultrasound
The role of breast ultrasound has expanded considerably as the technique and resolution of the equipment have improved. With high-frequency linear array transducers and higher resolution, smaller lesions and greater detail are visualized. The initial primary role of ultrasound was the differentiation of solid versus cystic masses (1,2,3,4). Sonography is ideal for this role and is important in planning the management of the patient. The roles of ultrasound are shown in Table 17.1.
Of paramount importance in incorporating ultrasound in a breast-imaging program is the use of high-quality equipment and proper technique. High-frequency linear array transducers are typically used. Current transducers have frequency ranges of 15-18 MHz, 13-8 MHz, 12-5 MHz and 10-5 MHz (5). Setting the focal zone to the proper depth, at the level of the area of interest, optimizes the analysis of the lesion of interest. Setting the power and time-gain compensation at the proper level is extremely important so that the analysis of cystic versus solid masses is accurate. If the gain is set too low, a hypoechoic solid mass may be interpreted as anechoic and thought to be a cyst when in fact it is solid. Scanning may be performed in a longitudinal and transverse pattern or in a radial and antiradial orientation (5).
The ACR BI-RADS® Lexicon for Breast Imaging (6) also has descriptions for ultrasound reporting. In the BI-RADS® for ultrasound, the following are described: background echotexture, mass features, calcifications, special cases, and vascularity. Masses are described (6) according to their shape, orientation, margins, lesion boundary, echo pattern, posterior acoustic enhancement features, and
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effect on surrounding tissue. The background echotexture may be homogeneous-fat, homogeneous-fibroglandular, or heterogeneous.
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TABLE 17.1 The Roles of Ultrasound |
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Mass shapes may be oval, round, or irregular, and their orientation is parallel or not parallel to the chest wall. The margination of masses may be described as circumscribed or not circumscribed (indistinct, angular, microlobulated, or spiculated). The boundary of the lesion may be abrupt, or the mass may be surrounded by an echogenic halo. These findings parallel mammographic findings in terms of the likelihood of benign versus malignant etiologies.
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Figure 17.1 HISTORY: A 34-year-old woman with a small palpable mass in the left breast at 9 o'clock. IMAGING: Left CC view (A) shows heterogeneously dense tissue and a BB marking a palpable lump. In addition, there is a vague rounded asymmetry located lateral to the nipple (arrow). Ultrasound of these areas showed two simple cysts (B,C). The cysts are anechoic, thin-walled, and very well defined, all of which are features of a simple cyst. IMPRESSION: Simple cysts, BI-RADS® 2. |
The echogenicity of masses may be described as anechoic, hyperechoic, hypoechoic, or isoechoic relative to the surrounding parenchyma, or they may be complex. Posterior acoustic features may be described as shadowing, enhancement, or no effect. Observation of the effect on surrounding tissue may include the following: ductal extension, changes in Cooper's ligaments, edema, architectural distortion, skin thickening, or skin retraction (6).
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Assessment of Isodense Circumscribed Masses: Cystic Versus Solid
The diagnosis of a simple cyst with ultrasound is very accurate and has been reported to range from 96% to 100% (1,2,3,4,7). Careful scanning technique that includes proper gain, transducer frequency, and resolution of the equipment is necessary in order to achieve this highly reliable differentiation of solid versus cystic lesions. In addition, the criteria for a simple cyst must be adhered to in order to confirm that a lesion is clearly benign. The criteria for a simple cyst are as follows: smooth thin walls, no internal echoes (anechoic), and posterior acoustic enhancement (Figs. 17.1,17.2,17.3). With compound imaging where the scan
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plane is multidirectional, posterior acoustic enhancement may not be observed for some small cysts.
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Figure 17.2 HISTORY: A 52-year-old woman who presents with left breast pain and a history of cysts in the past. IMAGING: Left MLO (A) and CC (B) views show the breast to be heterogeneously dense. Multiple round circumscribed masses are present, all of which were stable, except for a 3-cm mass in the left axillary tail (arrow) that was new. Because of the interval change in the left axillary tail mass, ultrasound of this region was performed. Sonography at the 2 o'clock position (C,D) shows the mass to be very well defined, oval, and anechoic, with a thin wall and posterior acoustic enhancement. All these features meet the criteria for a simple cyst. IMPRESSION: New mass left axillary tail, simple cyst, BI-RADS® 2. |
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Figure 17.3 HISTORY: A 48-year-old woman for screening mammography. IMAGING: Left MLO (A) and CC (B) views show the breast to be fatty replaced. There is a small, round, somewhat dense mass in the left subareolar area (arrows). Spot compression CC view (C) shows the mass to be circumscribed, suggesting that it is most likely benign. The mass was larger in comparison with prior studies, and because of this interval change, ultrasound was performed. Left breast sonography (D) shows that the mass is very well defined and anechoic, with a thin wall, all features of a simple cyst. IMPRESSION: Simple cyst, left breast, BI-RADS® 2. |
Importantly, the presence of acoustic enhancement behind a round or oval mass does not necessarily indicate that it is a cyst. Solid homogeneous masses, including breast cancers, may have acoustic enhancement as well. All the above-noted criteria must be met to call a mass a simple cyst. Thin septae may be present in a cyst and do not require biopsy. However, thick septae, a thick wall, or an intracystic solid component raises the concern for malignancy, and these findings do require tissue sampling (1,8).
Complicated cysts are those that contain low-level echoes. This may occur secondary to hemorrhage or inflammation or because the fluid is very thick (Fig. 17.4). Occasionally a very hypoechoic solid mass may have the appearance of a complicated cyst. Aspiration is usually performed when this finding is observed, especially if the mass is new, larger, or solitary. In a study of 150 cystic lesions, Berg et al. (9) found that none of the 38 complicated cysts that were aspirated proved to be malignant. Sebaceous cysts most often have the appearance of complicated cysts (Fig. 17.5), and because of their superficial location, their etiology is evident. Also, with sebaceous cysts, a thin track between the cyst and the skin surface is often visible.
Complex masses are those that contain both cystic and solid components. A thick rind around a cystic center, polypoid solid projections within a cystic mass, or a mass that has both fluid and solid components is complex. Such masses may represent necrotic tumors or intracystic benign or malignant tumors, but they also may represent several benign lesions. A cyst with marked inflammation or hemorrhage and clot may have this appearance. Similarly,
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abscesses and hematomas usually appear as complex masses (Figs. 17.6 and 17.7). The management of a complex mass usually requires biopsy unless the finding is clearly a hematoma. Berg et al. (9) found that 7/23 complex masses with thick walls or thick septae and 4/18 lesions with an intracystic solid component proved to be malignant. Intracystic papillary carcinomas and necrotic high-grade malignancies may appear as complex masses on sonography (Figs. 17.8,17.9,17.10). Sampling of the solid portion of the mass is important, rather than aspiration of the fluid, so ultrasound has an important role in guiding the biopsy. Either percutaneous biopsy directed at the solid component of the mass or excision of the entire lesion is usually performed for diagnosis.
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Figure 17.4 HISTORY: A 58-year-old woman with bilateral palpable masses. IMAGING: Right ML (A) and CC (B) magnification views show dense parenchyma and scattered benign calcifications. There is a large round mass in the right subareolar area with a well-circumscribed margin and a fatty halo (arrow), suggesting a benign etiology. In the left breast in the area of palpable concern, the spot compression CC (C) and ML (D) views show the palpable mass to be high density, irregular, with spiculated margins, and suspicious for malignancy. Right breast ultrasound (E) shows the round mass to be circumscribed and to contain low-level echoes suggesting a complicated cyst. The left breast ultrasound (F) shows the palpable mass to be irregular, hypoechoic, and shadowing and to have a branching ductal pattern in its periphery, highly suspicious for malignancy. IMPRESSION: Right breast complicated cyst, left breast carcinoma. HISTOPATHOLOGY: Right cyst aspiration showing benign-appearing green fluid. Left breast core biopsy showing invasive ductal carcinoma. |
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Figure 17.5 HISTORY: A 33-year-old woman with a small palpable mass in the left breast at 7 o'clock. IMAGING: Mammography showed no abnormality to correspond with the palpable lesion. On ultrasound (A,B) the mass is complex, round, and located in the cutaneous area. The superficial fascial plane is not visible over the lesion, indicating that the mass is in the skin. A small track from the mass (arrow) is contiguous with the skin (B). IMPRESSION: Sebaceous cyst. |
A solid mass on ultrasound is analyzed based on its contour, margination, orientation, and echogenicity. Although ultrasound cannot definitely diagnose a solid lesion as benign or malignant, there are criteria that are helpful in predicting a benign versus a malignant etiology. These features are based on the nature of benign masses, such as fibroadenomas, which are homogeneous lesions that have an encapsulated, very-well-defined margin (Figs. 17.11,17.12,17.13,17.14). Stavros et al. (10,11) described the criteria for solid benign versus malignant masses. The features of benign solid masses are listed in Table 17.2.
The sonographic features of fibroadenomas have been described in early papers (12,13) as hypoechoic, oval masses. Fibroadenomas are very well defined with a thin margin, and occasionally a pseudocapsule is evident. The lesions are usually elongated and wider than tall in orientation. Sometimes thin hyperechoic septae are seen with fibroadenomas. Most fibroadenomas have no effect on sound transmission, but some may enhance or shadow. When shadowing is identified, or when the orientation is not elongated or the borders are not well defined, biopsy is performed. A lesion that may have a similar appearance to a fibroadenoma is a phylloides tumor. On mammography, a large circumscribed mass is seen; on ultrasound, the mass is typically circumscribed and hypoechoic. The epithelial-lined clefts inside the mass may appear as small cystic spaces within the solid lesion on ultrasound (Fig. 17.15) (14).
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TABLE 17.2 Ultrasound Features of Benign Solid Masses |
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Figure 17.6 HISTORY: A 43-year-old patient with a history of trauma to the breast and a small palpable lump. ULTRASOUND: Ultrasound of the lump demonstrates a complex mass, which has irregular margins extending along tissue planes. Within the mass is a solid-appearing component. IMPRESSION: Complex mass consistent with organizing hematoma. NOTE: Follow-up sonography in 1 to 3 months should be performed to confirm resolution of the hematoma and to verify that there is no residual mass. |
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Figure 17.7 HISTORY: A 27-year-old woman with a tender palpable right breast mass. She had been treated with antibiotics and the mass had not resolved. MAMMOGRAPHY: Right breast ultrasound over the lump shows it to be complex in appearance. Portions (A) of the mass are lobulated, of mixed echogenicity, and with some extensions into the tissue. Other portions appear more loculated and fluid filled (B). There is surrounding hyperechoic edema. Mammography was performed and was noncontributory. The patient underwent vacuum-assisted biopsy of the area, and a large amount of purulent material was aspirated, along with the tissue specimen. HISTOPATHOLOGY: Granulomatous inflammation. NOTE: The patient underwent subsequent surgical drainage of the abscess and antibiotic therapy, and the area resolved. |
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Figure 17.8 HISTORY: A 51-year-old woman with a palpable mass in the left breast at 6 o'clock. IMAGING: Left ML view (A) shows a dense breast with benign eggshell calcification in the subareolar area (arrow). The palpable mass is not seen on mammography. On ultrasound (B), the palpable mass is observed and is complex, having a partially cystic component as well as an intracystic filling defect. IMPRESSION: Intracystic lesion, papilloma versus carcinoma. HISTOPATHOLOGY: Sclerotic intracystic papilloma. |
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Figure 17.9 HISTORY: A 61-year-old woman with a history of a mass in the left breast, for further evaluation. IMAGING: Left breast ultrasound (A,B) shows the palpable mass to be complex. The wall is thick and slightly irregular, and there is a cystic component as well. Parts of the mass appear more solid (B, arrow), suggesting the presence of an intracystic mass. Alteratively, this could be a necrotic tumor or an abscess. Core needle biopsy with a vacuum probe was performed. IMPRESSION: Complex mass, suspicious for carcinoma. HISTOPATHOLOGY: Invasive ductal carcinoma with papillary features. |
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Figure 17.10 Ultrasound image of a palpable mass shows it to be complex. Portions are fluid filled, but the lateral wall is thickened with a solid component (arrows). Excision showed intracystic papillary carcinoma. (Case courtesy of Dr. Christine Denison, Boston, MA. ) |
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Figure 17.11 HISTORY: A 26-year-old woman with a new palpable breast mass. IMAGING: Ultrasound shows the mass to be solid and to have benign features. It is well circumscribed, hypoechoic, and oval. There is a thin echogenic pseudocapsule surrounding the mass. Because the mass was new and palpable, it was biopsied. IMPRESSION: Solid mass, likely a fibroadenoma. HISTOPATHOLOGY: Fibroadenoma. |
Lesions that are hyperechoic on ultrasound are typically those that contain fat. Hyperechoic masses include the following: fat necrosis (Figs. 17.16 and 17.17), lipomas, hamartomas, angiomas (Fig. 17.18), and focal fibrosis. The appearance of fat necrosis ranges from anechoic masses to complex masses with mural nodules to solid masses of varying echogenicity (15). Lymph nodes also are hyperechoic in part, depending on the amount of fatty replacement. Normal nodes are elliptical and have a smooth cortex that is hypoechoic and a bright hyperechoic center that is the fatty hilum (16) (Fig. 17.19). Abnormal nodes have a thickened cortex and an indistinct margin, and they may have an increased anteroposterior (AP) diameter with obliteration of the fatty hilum (Fig. 17.20).
Based on the Stavros et al. (10) criteria, the likelihood of a solid mass with benign characteristics actually being benign is greater than 98%. Therefore, for a nonpalpable circumscribed mass on mammography that has benign sonographic features, early follow-up may be performed. However, for new palpable or enlarging solid masses, even with benign features, biopsy is usually performed for confirmation.
Malignancies tend to be more indistinct in margination and more firm, so their AP diameter is often greater than their transverse diameter. The features of malignant masses on ultrasound are listed in Table 17.3. Malignant masses may be markedly hypoechoic, irregular (17) shadowing lesions (Figs. 17.21,17.22,17.23,17.24). Because of the dense stromal reaction, the posterior acoustic shadowing with cancers may be intense. Some cancers have branching
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linear extensions around their borders, which may indicate intraductal extension of tumor. Angular or microlobulated margins are also suspicious features for malignancy. A vertical orientation (taller than wide) is an ominous sign and has a high positive predictive value of being malignant (18,19). The highest positive predictive values for malignancy on the ultrasound of masses have been found to be the following findings: spiculation (87%), a thick hyperechoic halo (74%), and a taller-than-wide orientation (74%). The lowest predictive values of the malignant signs were associated with microlobulations and ductal extension (11).
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TABLE 17.3 Sonographic Features of Malignant Solid Masses |
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Figure 17.12 HISTORY: A 53-year-old woman with a palpable mass and a negative mammogram. IMAGING: Single ultrasound image over the palpable mass shows it to be hypoechoic, oval, and well defined, features suggestive of a fibroadenoma. Because it was palpable, biopsy was performed. HISTOPATHOLOGY: Fibroadenoma. |
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Figure 17.13 HISTORY: A 47-year-old woman recalled from screening mammography for right breast calcifications. IMAGING: Right ML magnification view (A) shows a lobular mass that contains circumscribed margins in the subareolar area (arrow). The mass has associated amorphous microcalcifications. Right breast ultrasound (B) shows the mass (arrow) to be oval, elongated, and well defined. There are some bright echoes within the lesion, likely related to the calcifications observed on mammography. Core needle biopsy was performed using ultrasound guidance. HISTOPATHOLOGY: Fibroadenoma. |
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Figure 17.14 HISTORY: A 39-year-old woman recalled for a left breast mass found on screening mammography. IMAGING: Left CC magnification view (A) shows a lobulated isodense mass located medially, having borders that are partially circumscribed and partially obscured. Because of this finding, ultrasound was performed. Sonography (B,C) reveals a hypoechoic, lobular mass that is partially defined. The lesion has multiple lobulations, and on some images, it has a slight indistinctness of the margins. Although this may represent a fibroadenoma, the sonographic features are not clearly benign. Biopsy was therefore performed. HISTOPATHOLOGY: Fibroadenoma. |
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Figure 17.15 HISTORY: A 25-year-old woman with a new palpable right breast mass. ULTRASOUND: Ultrasound of the palpable mass shows it to be oval, elongated, and smoothly marginated. The echo pattern is somewhat inhomogeneous. The shape of the mass suggests a fibroadenoma, particularly for a patient in this age group. IMPRESSION: Solid mass, likely a fibroadenoma; recommend biopsy to confirm. HISTOPATHOLOGY: Benign phylloides tumor. NOTE: Phylloides tumors often have a heterogeneous echo pattern related to the cystic spaces within the stroma. |
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Figure 17.16 HISTORY: A 43-year-old woman with a small palpable mass in the left breast. IMAGING: Left CC view (A) shows scattered fibroglandular tissue and a BB marking the palpable area of concern. No mammographic finding is present. Ultrasound (B,C) shows the palpable lesion to be heterogeneous in appearance. The periphery is hyperechoic, and the center is markedly hypoechoic and oriented obliquely toward the skin. The features are most suggestive of an area of resolving hematoma and fat necrosis. The patient had a vague history of recent trauma to this region. The area was followed in 4 weeks with ultrasound, and it resolved. IMPRESSION: Fat necrosis, resolving hematoma. |
Some cancers, particularly medullary or mucinous carcinomas, have a pushing edge and are homogeneous on ultrasound. These tumors may look round and smooth and be very hypoechoic, and because of the homogeneity of the mass, they may be associated with posterior acoustic enhancement. One must use great care in order not to misinterpret a medullary or a mucinous malignancy as a cyst. Also, some very-high-grade cancers or necrotic cancers may have this same appearance. Often in these cases, though, the orientation of the lesion is vertical rather than elongated or horizontal, as is seen in benign lesions.
A variety of benign conditions may have sonographic features that are indeterminate or frankly suspicious for malignancy. Prominent shadowing is associated with dense stromal areas that may be seen in scars, focal fibrosis, hyalinized fibroadenomas, and diabetic fibrous mastopathy (Fig. 17.25). Hypoechoic masses that are not completely circumscribed or that are inhomogeneous are
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seen in fibrocystic conditions at times. Radial scars (Fig. 17.26) and papillomas may also appear as solid masses that are not clearly benign.
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Figure 17.17 HISTORY: A 36-year-old woman with a new left breast palpable mass. IMAGING: Left MLO (A) and CC (B) views with a BB over the palpable lump show a fatty-replaced breast, with no mammography abnormality. Sonographic image (C) of the palpable mass shows it to be well defined, hyperechoic, with areas of hypoechogenicity(arrows). This lesion is located very superficially, a finding often seen in posttraumatic lesions. The findings are most suggestive of fat necrosis because of the negative mammogram and the sonographic findings. IMPRESSION: Palpable mass, possible fat necrosis; recommend biopsy. HISTOPATHOLOGY: Recent hemorrhage with fat necrosis. |
An algorithm for the management of solid breast masses based on their sonographic features has been described by Stavros et al. (11). Based on this algorithm, one must first assess the lesion for any suspicious features. If a single suspicious feature is present, biopsy should be performed. If there are no suspicious features, one must search for benign characteristics. If there are no benign findings, classify the lesion as BI-RADS® 4A, suspicious, and perform a biopsy. If all the features are benign, the lesion is likely benign, and one can perform an early follow-up ultrasound.
Ultrasound in the Evaluation of the Palpable Mass
Breast ultrasound plays a critical role in the assessment of the patient with a palpable lump. For patients with a lump that is visible on mammography as a circumscribed mass, ultrasound differentiates cystic from solid etiologies. In the past, before percutaneous breast biopsy was widely used, a suspicious mass on mammography was not evaluated with ultrasound (4). However, both nonpalpable and palpable suspicious masses are often now imaged sonographically to determine if they are visible and if they can be biopsied with ultrasound guidance.
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Figure 17.18 HISTORY: Postmenopausal patient recalled from screening mammography for a mass in the left breast. MAMMOGRAPHY: Spot compression view (A) of the mass that was identified on screening shows the lesion to be isodense and to have microlobulated margins. The borders are somewhat suspicious for malignancy. Ultrasound (B) of the lesions shows it to be hyperechoic and oval and relatively well defined, suggesting most likely a benign etiology. Core needle biopsy was performed, based on the mammographic finding. HISTOPATHOLOGY: Capillary angioma. NOTE: Angiomas and other vascular lesions may be markedly hyperechoic on ultrasound. |
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Figure 17.19 HISTORY: A 42-year-old woman with a small palpable breast mass in the upper outer quadrant. IMAGING: Mammography was negative. Ultrasound of the mass shows an oval, hypoechoic circumscribed mass with a hyperechoic center consistent with the fatty hilum of a lymph node. IMPRESSION: Intramammary node, BI-RADS® 2. |
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Figure 17.20 HISTORY: A 65-year-old woman with a history of left breast cancer treated with mastectomy, axillary node dissection, and chemotherapy 12 years ago. She now presents with a palpable mass in the left axilla. ULTRASOUND: Sonography (A,B) of the left axilla shows a lobular mass that is taller than wide. The margins are partially circumscribed. The periphery of the mass is hypoechoic, and the center is hyperechoic, indicating that it is a lymph node. The size and contour of this node are abnormal. The widened nodular cortex of the node is suspicious for malignancy. Needle biopsy was performed using ultrasound guidance. HISTOPATHOLOGY: Metastatic carcinoma consistent with primary breast cancer. |
In the patient with a palpable mass and with vague, nonspecific mammographic findings or a negative mammogram, ultrasound is the next step in evaluation. Ultrasound may demonstrate a cancer or a benign mass that is not evident on mammography (Fig. 17.27). Various studies have shown the value of ultrasound in demonstrating palpable cancers that are mammographically occult (4,20,21,22,23,24).
In addition, a negative ultrasound is an important factor in determining the patient's management. A negative ultrasound and negative mammogram in the clinical situation of a palpable mass are associated with a risk of malignancy of <2%. Depending on the level of suspicion on clinical exam, clinical follow-up rather than biopsy may be performed when imaging is completely negative (25).
Ultrasound in Young or Pregnant Patients
In women younger than age thirty with a palpable mass, the most likely diagnosis is a fibroadenoma, with cysts and cancers being less likely. The workup of the patient is affected by the very low frequency of cancers is this age group and by the somewhat increased radiosensitivity of the breasts. Typically, mammography is not performed first, unless the patient is at high risk for breast cancer.
Most breast imagers (4,18,26,27) begin with ultrasound in the symptomatic young patient (Fig. 17.28). The exception to this is the very-high-risk patient (BRCA1 or BRCA2 carrier, history of treated Hodgkin disease, strong premenopausal family history, personal history of breast cancer). In the very-high-risk patient, bilateral mammography is performed first. A pitfall in this age group is the assumption that the patient has very dense breasts and that mammography is not helpful or will not detect cancer. Often in young women with breast cancer, a delay in diagnosis occurs for this reason (28).
In the usual-risk patient, ultrasound is performed to determine if the palpable mass is solid, cystic, or not seen. If the lesion is a cyst, no further workup is needed. If the lesion is solid and has the appearance of fibroadenoma, or if the lesion is clearly palpable but not seen on ultrasound, the next step is mammography. The mammographic examination may be limited to imaging the ipsilateral breast if the lesion does not have suspicious sonographic features. For a solid lesion that has any malignant features on ultrasound, bilateral mammography is usually performed. For new solid palpable masses, needle biopsy is typically performed for diagnosis, even if the lesion has an appearance suggestive of a fibroadenoma.
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Figure 17.21 HISTORY: Screening mammogram on a 60-year-old woman. IMAGING: Right MLO (A) and CC (B) views show heterogeneously dense tissue and scattered benign calcifications. At 6 o'clock, there is a dense, round, relatively circumscribed mass. Ultrasound (C) shows the mass to be markedly hypoechoic, round, and taller than wide. The anterior margin is slightly irregular and angulated. This mass should not be confused with a cyst because it is nearly anechoic. The worrisome features here are the vertical orientation and the indistinct anterior margin. IMPRESSION: Markedly hypoechoic round mass, suspicious for carcinoma. HISTOPATHOLOGY: Invasive ductal carcinoma. |
In pregnant patients, ultrasound is also usually performed first. Limiting the radiation exposure is important, so depending on the ultrasound findings, mammography may be delayed until the second trimester of pregnancy. If, however, the sonographic finding has any aspects suspicious for malignancy, complete evaluation is needed without a delay. In pregnant patients, fibroadenomas, lactating adenomas, accessory breast tissue, galactoceles, and cancers occur. Because of the hormonal milieu, fibroadenomas may grow in these patients. Cancers also may grow more rapidly, so care must be taken not to delay the diagnosis of a suspicious mass.
In lactating patients, palpable masses are often abscesses or galactoceles; however, lactating adenomas, fibroadenomas, and cancers occur as well (Figs. 17.29 and 17.30). Depending on the age and family history of the patient, ultrasound is often performed first. If ultrasound demonstrates a cyst, no further workup is necessary. For an apparent abscess, and depending on the level of symptoms, treatment may be performed before mammography. For solid masses, mammography and further evaluation with biopsy are performed. For patients older than age 30, mammography is usually performed first.
Imaging of Asymmetries and Calcifications
Traditionally, focal asymmetries that are nonpalpable and identified on mammography have been managed based on their mammographic characteristics. For focal asymmetric densities or for questionable architectural distortion, ultrasound may be of value in trying to identify the presence of a mass. An ultrasound-detected mass within an area of mammographic asymmetry confirms that a true lesion is present and prompts biopsy (Figs. 17.31 and 17.32). In addition, sonographic guidance can be used to target the density, which sometimes can be difficult to target accurately with stereotaxis. When ultrasound is
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negative for a mass, the asymmetry must be managed based on its mammographic characteristics.
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Figure 17.22 HISTORY: A 40-year-old woman with a palpable mass in the left breast inferiorly. IMAGING: Left ML spot view (A) shows a high-density mass with microlobulated margins, highly suspicious for malignancy. On ultrasound (B), the mass is of mixed echogenicity and has irregular margins with branching ductal extensions. IMPRESSION: Highly suspicious for carcinoma. HISTOPATHOLOGY: Infiltrating ductal carcinoma and DCIS, with one positive node. |
Microcalcifications may occasionally be seen on high-resolution ultrasound but most often are not visible. Therefore, sonography is not used to evaluate the etiology of microcalcifications. However, performing breast ultrasound is most helpful in planning interventions and management in one circumstance. When microcalcifications having a suspicious appearance for ductal carcinoma in situ (DCIS) are present, particularly when the area is larger than a cluster, ultrasound is a helpful adjunct to mammography (Fig. 17.33).
The most likely diagnosis for BI-RADS® 5 microcalcifications is DCIS. If needle biopsy is performed and demonstrates DCIS, lumpectomy without an assessment of the axilla is performed. If final pathology on the excision shows invasive carcinoma also, the axillary nodes are then sampled in a second surgery. The preoperative identification of invasive carcinoma is important in surgical planning in that lumpectomy with axillary node sampling is performed as one procedure. Ultrasound may demonstrate a solid mass within a region of calcifications, and this finding suggests the presence of an invasive cancer. Therefore, percutaneous ultrasound-guided biopsy of the mass is most helpful in treatment planning.
Screening Ultrasound
The role of ultrasound in the detection of clinically occult breast cancer remains uncertain. Early literature using a water path scanner (20,29) found that screening ultrasound was not an acceptable substitute for mammography to detect breast cancer. Small nonpalpable breast cancers were not adequately identified with ultrasound.
With significant improvements in the ultrasound technology and with better resolution, greater detail is available, and small cancers are identifiable. Since 1995, several studies (30,31,32,33,34,35) have evaluated the value of screening ultrasound, primarily in women with dense parenchyma on mammography. The prevalence of cancers detected by ultrasound alone in these series ranged from 0.27% to 0.9%, and the mean tumor size ranged from 9.0 to 11.0 mm (36).
In an analysis of the 42,838 screening ultrasound examinations reported in six series, Feig (36) calculated a positive predictive value in biopsies performed based on a suspicious ultrasound examination of 11.4%. This is less than the literature shows for mammographically detected lesions but is certainly not an insignificant number. In one of the largest series, Kolb et al. (32) found 246 cancers on screening ultrasounds of 11,130 asymptomatic women with dense breasts and negative mammography. The authors found that mammographic sensitivity declined with increasing breast density and that screening ultrasound increased the detection of small early-stage breast cancers.
In addition to a true screening ultrasound in the patient with negative mammography, ultrasound may be performed to assess the extent of carcinoma by searching for other mammographically occult cancers (Fig. 17.34). Full breast ultrasound imaging has been shown to be useful in identifying other mammographically and clinically occult foci of tumor in the patient with a known breast cancer in the ipsilateral breast (37). Although MRI is more
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frequently used in this role, ultrasound may be helpful initially or as a second-look procedure. The cost of ultrasound is less than that of MRI, and if multicentric disease is identified, the clinical plan for breast is not changed by adding MRI. If MRI detects a mammographically occult lesion that is not clinically apparent and that is suspicious for multifocal or multicentric carcinoma, biopsy is necessary. With knowledge of the location and size of the lesion, a second-look ultrasound may identify the abnormality, which can then be biopsied more easily with ultrasound guidance. LaTrenta et al. (38) found an ultrasound correlate for 23% of suspicious lesions identified on MRI.
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Figure 17.23 HISTORY: Premenopausal woman with a palpable mass in the left breast at 6 o'clock. MAMMOGRAPHY: Left MLO (A) and CC (B) views show heterogeneously dense tissue. There is an irregular mass with indistinct margins located inferiorly (arrow). Ultrasound (C) shows the mass to be microlobulated, markedly hypoechoic, and taller than wide. This mass has very suspicious features on sonography, and it should not be confused with a cyst because it is so hypoechoic. IMPRESSION: Highly suspicious for carcinoma. HISTOPATHOLOGY: Invasive lobular carcinoma. |
Occasionally, mammographically occult cancers are identified incidentally. When an ultrasound is performed as a diagnostic test to evaluate a particular lesion or lesions, scanning adjacent tissue or the rest of the breast may lead to the observation of an abnormality that is suspicious. If such a lesion is identified, further evaluation is needed, because a mammographically occult carcinoma certainly may be present (Fig. 17.35).
Implant Imaging
The imaging of patients with augmented breasts with silicone prostheses may include ultrasound to search for rupture. The specificity for ultrasound in the identification of implant rupture has been reported to range from 55% to 79%, and sensitivity is 59% to 85% (18,39,40,41). Both intracapsular rupture and extracapsular rupture can be identified on ultrasound, whereas mammography does not show intracapsular rupture. MRI is also of great value in the assessment of implants for rupture.
The normal implant has an anechoic appearance on ultrasound. A prominent reverberation artifact is visible
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in the anterior aspect of the implant. Radial folds are often visible as linear bands connecting to the implant wall. Setting the focal zone and depth to an appropriate level to image through the implant and the use of a lower frequency transducer at times is necessary for adequate visualization and assessment of the prosthesis.
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Figure 17.24 HISTORY: A 41-year-old patient with a palpable mass in the 12 o'clock position of the right breast. IMAGING: Right CC view (A) shows a large, dense spiculated mass centrally (arrow). Adjacent to this mass is a smaller spiculated lesion (arrowhead), and there is a dense lobular mass in the lateral aspect of the breast. Sonography of the right breast (B) shows a large dense mass (arrows) centrally that is producing very prominent shadowing, corresponding to the palpable mass noted on mammography. Adjacent to this lesion is a small irregular mass (arrow) with very prominent central shadowing (C). The lateral lesion (D) is more rounded and slightly indistinct in margination. The internal echo texture is homogeneous and hypoechoic. Each of these lesions has different sonographic features of malignancy. HISTOPATHOLOGY: Multicentric invasive ductal carcinoma. |
When an intracapsular rupture occurs, the implant wall is broken, but the silicone remains contained within the fibrous capsule that the body forms around the implant. In this situation, the broken wall of the implant is floating within the silicone. The wall structure is visible on ultrasound as multiple parallel linear echoes in a stair-step pattern. These correspond to the so-called linguine sign on MRI. Diffuse internal echoes may also be seen in the case of intracapsular rupture.
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Figure 17.25 HISTORY: A 34-year-old insulin-dependent diabetic woman with a palpable right breast mass. Clinical exam showed firm tissue in the right periareolar area. IMAGING: Bilateral MLO (A) and CC (B) views show dense parenchyma bilaterally, with no focal abnormality. A BB marks the palpable abnormality on the right. On the right breast ultrasound (C), very dense acoustic shadowing is seen, suspicious for carcinoma. Sonography of the left breast (D) shows a similar pattern. IMPRESSION: Dense shadowing bilaterally, likely diabetic fibrous mastopathy. HISTOPATHOLOGY: Fibrous mastopathy. |
When the rupture extends beyond the fibrous capsule, an extracapsular rupture is present. This may be evident on mammography as droplets of silicone beyond the apparent implant lumen. On ultrasound, “silicone cysts” may be evident as small, hypoechoic nodules beyond the confines of the prosthesis. With the intense tissue reaction to the silicone, a characteristic feature is seen on ultrasound: the snowstorm appearance (42,43,44) (Figs. 17.36 and 17.37), which is echogenic noise or shadowing related to the tissue's reaction to silicone.
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Figure 17.26 HISTORY: A 48-year-old woman with a palpable mass in the right breast. IMAGING: Mammography showed dense breast tissue and did not reveal the mass. On ultrasound, the lesion is hypoechoic and of mixed echogenicity; the shape of the mass is lobular, its borders are partially defined, and its orientation is elongated. These findings suggest a fibrocystic etiology, but carcinoma can not be excluded. IMPRESSION: Solid mass, BI-RADS® 4; recommend biopsy. HISTOPATHOLOGY: Radial scar. |
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Figure 17.27 HISTORY: A 58-year-old woman with a history of left mastectomy. She reports a new palpable right subareolar mass. IMAGING: Right CC view (A) shows heterogeneously dense tissue with vague increased density in the subareolar region. Ultrasound (B) was performed to evaluate the palpable mass. Sonography shows the lesion to be taller than wide, indistinct and hypoechoic with acoustic enhancement. The orientation and borders of the lesion are suspicious for malignancy. HISTOPATHOLOGY: Invasive ductal carcinoma. NOTE: Sonography of a palpable mass should be performed if mammography is negative or equivocal. Particularly when the parenchyma is dense, a noncalcified lesion may be obscured on mammography. |
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Figure 17.28 HISTORY: A 25-year-old woman with a 3-day history of a tender firm mass in the left breast. She had been gardening on the day of onset of the mass but she had not noticed any injury. IMAGING: Left ultrasound was performed first because of the age of the patient. Sonography of the palpable mass (A) shows it to be round, slightly indistinct, and heterogeneous in echo pattern. The differential includes carcinoma versus an inflamed cyst versus abscess versus hematoma. Left mammography was performed before biopsy. Left MLO (B) and CC (C) views show the breast tissue to be dense, compatible with the patient's age. A BB marks the palpable mass at 12 o'clock, which is lobular, isodense, and obscured. Vacuum-assisted core needle biopsy was performed using ultrasound guidance. Purulent material was retrieved along with the core tissue sample. HISTOPATHOLOGY: Acute and chronic mastitis with granulation tissue. NOTE: The abscess was drained via the vacuum-assisted biopsy probe and resolved with antibiotic therapy. |
Breast Interventions
Ultrasound has played an extremely important role in guiding breast interventions (45). With sonographic guidance, needle localization, cyst aspiration, fine-needle aspiration biopsy, core biopsy, and vacuum-assisted biopsy can be performed (46,47,48). The technology has evolved and the needles and devices have been developed to offer a variety of choices for tissue diagnosis.
Advantages of ultrasound for percutaneous biopsy are many. The lack of radiation, the ease of positioning the patient, and patient comfort (49) are evident to the patient as advantages. The equipment is multiuse and not strictly used for biopsy. The cost of equipment is less than stereotactic equipment, and the cost of the procedure is less (50). The accuracy of tissue sampling is great, and the ability to observe the needle trajectory as the sample is acquired in real time is important in assessing an adequate and accurate sample. The ability to visualize the lesion and rapidly aspirate or sample it leads ultrasound guidance to be the procedure of choice for many interventionists.
The Role of Magnetic Resonance Imaging of the Breast
The clinical roles of breast MRI include the following:
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Figure 17.29 HISTORY: A 32-year-old woman with no family history of breast cancer who is 2 months postpartum and who presents with a firm right breast mass. MAMMOGRAPHY: Right ML (A), CC (B) and spot ML (C) views show the breast to be extremely dense, compatible with a lactating state. There is a focal area of increased density having a very glandular appearance (arrows) corresponding to the palpable mass at 5 o'clock. Clinical examination demonstrated a very firm, glandular region in the right inner-lower quadrant. The patient reported that she had always had this fullness, but it had become more masslike since her delivery. Ultrasound (D,E) showed multiple dilated ducts that extend up to the skin line throughout the palpable region. No solid mass was identified. IMPRESSION: Accessory breast, stimulated by breastfeeding. NOTE: The accessory breast that does not have a communication to the skin can become quite engorged during lactation. |
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Figure 17.30 HISTORY: A 33-year-old lactating patient with a red, tender right breast. MAMMOGRAPHY: Right ML (A) and CC (B) views show extremely dense tissue compatible with a lactating state. The area marked by the BB as palpable is generally more dense, but no definite finding is identified otherwise. On ultrasound (C), there is a complex mass in the subareolar area corresponding to the lump. This mass appears to have some thick internal septations and is partially fluid filled. The edges are somewhat indistinct. Given the history and physical findings, this most likely represents an abscess. The patient was treated with drainage and antibiotics, and the abscess resolved. IMPRESSION: Abscess in a lactating breast. |
These clinical recommendations were defined by the Interventional Working Group on Breast MRI in 2004 (51).
The technique for MRI imaging for tumor assessment includes the use of a breast coil and a 1.5T magnet, and dynamic imaging with injection of gadolinium DTPA. High resolution with an in-plane resolution of 1 mm or less and a slice resolution of 2 mm or less are recommended (51). A challenge for breast MRI is to achieve a high temporal resolution in conjunction with a high spatial resolution. The temporal resolution is needed in order to be able to scan rapidly and repetitively, and to assess for neovascularity, patterns of enhancement, and the washout of contrast. Biopsy capability is necessary so that when MRI-detected suspicious lesions are identified and are not visible on mammography or ultrasound, MRI-guided needle localization (52,53) or core biopsy can be performed (54,55).
Magnetic Resonance Imaging of Augmented Breasts
Early work with breast MRI was primarily for the evaluation of implant rupture. MRI has been shown (56,57,58,59) to be the most effective modality for the diagnosis of rupture. Silicone has a unique MRI frequency and a long T1 and T2 relaxation time. On T2-weighted images, silicone has a
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signal intensity greater than fat and less than water. The wall of the implant, composed of silicone polymer, is of lower signal intensity than the silicone gel contents (59).
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Figure 17.31 HISTORY: A 41-year-old woman for screening mammography. MAMMOGRAPHY: Bilateral CC views (A) show heterogeneously dense tissue. In the lateral aspect of the left breast, there is a lobulated, relatively circumscribed mass (arrow). When comparing the breasts as mirror images, an area of architectural distortion is also noted, superimposed over the dense tissue in the left breast medially (arrowhead). Ultrasound (B) of the lateral mass shows it to be hypoechoic and lobulated with features most compatible with a fibroadenoma. Sonography of the medial aspect of the breast (C) shows two masses: a complex cyst as well as a small solid mass that is associated with dense shadowing (arrow). IMPRESSION: Three masses likely representing a cancer, a fibroadenoma, and a complicated cyst. HISTOPATHOLOGY: Fibroadenoma (lateral mass), invasive ductal carcinoma (medial mass). |
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Figure 17.32 Spot compression view (A) performed for an area of asymmetry shows a small dense area of distortion centrally. Ultrasound (B) is helpful in this situation in confirming the presence of an irregular mass, suspicious for carcinoma. Also, sonographic guidance is an ideal method for directing percutaneous breast biopsy. HISTOPATHOLOGY: Invasive lobular carcinoma. |
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Figure 17.33 HISTORY: A 47-year-old woman who had been followed for 2 years for microcalcifications in the right breast and who now presents for a second opinion. IMAGING: Right ML magnification (A) and CC magnification (B) views show fine pleomorphic microcalcifications in a regional distribution in the upper inner aspect of the breast (arrows). These are highly suspicious for malignancy and do not meet the criteria for a probably benign lesion. Ultrasound was performed to search for an underlying mass. On ultrasound (C) of the area of microcalcifications, a mass is identified. The lesion is taller than wide, hypoechoic, and somewhat irregular, all features that are highly suspicious for malignancy. The presence of the mass raises the likelihood of an invasive component. Core needle biopsy of the mass was performed under sonographic guidance. IMPRESSION: Highly suspicious for malignancy. HISTOPATHOLOGY: Invasive ductal carcinoma, DCIS. |
The normal single-lumen implant has an oval shape and uniform signal intensity. Radial folds may be seen and represent infolding of the silicone wall or shell. These are linear invaginations that are of low signal and attach to the wall. Radial folds are a normal finding and do not indicate signs of rupture. Typically, radial folds have a sharp angulation with the fibrous capsule that helps to differentiate them from an intracapsular rupture, which is oriented parallel to the capsule (60).
In patients with an intracapsular rupture, the silicone shell is broken, and the silicone has extravasated into the space within the fibrous capsule. In these patients, the silicone shell is floating within the silicone and has the
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appearance of the linguine sign within the silicone. The low signal wall appears to float within the silicone gel (Figs. 17.38 and 17.39).
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Figure 17.34 HISTORY: A 42-year-old woman with a palpable mass in the left breast at 3 o'clock posteriorly. MAMMOGRAPHY: Left MLO (A) and CC (B) magnification views show a high-density spiculated mass with associated fine linear microcalcifications (arrow) that are highly suspicious for malignancy. This corresponded to the palpable mass. No other suspicious mass was noted on mammography, but the calcifications do extend in a ductal distribution from the mass anteriorly (B, arrowheads). Left breast ultrasound was performed to evaluate the palpable mass and the remainder of the breast. The palpable mass (C) is microlobulated, shadowing, hypoechoic, and taller than wide. The borders are indistinct, and there is some surrounding hyperechogenicity, compatible with edema, all of which are malignant features. In the subareolar area (D), a second solid irregular lesion that has indistinct margins and is also hypoechoic is seen. This lesion is also highly suspicious for malignancy. IMPRESSION: Multifocal carcinoma. HISTOPATHOLOGY: Invasive ductal carcinoma with DCIS at both sites. |
With extracapsular rupture, the silicone extends outside the capsule into the breast tissue and the axilla. Droplets of silicone are visible on MRI beyond the confines of the fibrous shell that is around the silicone (Fig. 17.40). Reported sensitivity and specificity of breast MRI for rupture have been retrospectively reported to be 94% and 97%, respectively (59). The most reliable signs of rupture are the linguine sign (59) and free silicone in the extracapsular area (59).
Problem-solving Magnetic Resonance Imaging
MRI is performed to assess the breast for malignancy in several important clinical situations. The technical considerations for tumor assessment include the following requirements: use of a breast coil, contrast administration, subtraction or fat suppression or both, T1- and T2-weighted sequences, scan thickness of no more than 3 mm, image acquisition time to allow for repeated scans through the same area in 60 to 90 seconds, and the ability to calculate time-intensity curves.
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Figure 17.35 HISTORY: A 38-year-old patient who presents with a small palpable mass in the right upper-outer quadrant. MAMMOGRAPHY: Right MLO (A) and CC (B) views showed dense parenchyma and no dominant mass. Ultrasound (C) was performed and showed a small cyst that corresponded to the palpable finding. More inferiorly in the same breast in an area that was not palpable, ultrasound (D) demonstrated an irregular solid mass with dense shadowing, highly suspicious for carcinoma. IMPRESSION: Right cyst that is palpable; right suspicious solid mass, an incidental finding. HISTOPATHOLOGY: Invasive lobular carcinoma. NOTE: Occasionally screening ultrasound or ultrasound of the remainder of the breast that is being evaluated for a specific finding will reveal a mammographically and clinically occult carcinoma. If a suspicious sonographic finding is observed, biopsy using ultrasound guidance is performed. |
Because of the tumor neovascularity and angiogenesis, the contrast rapidly flows into the area of the tumor. With arteriovenous shunting, there is a rapid washout of contrast. Because of this phenomenon, tumors tend to enhance rapidly and intensely compared with benign lesions. Because of the vascular characteristics of malignancy, the contrast also rapidly washes out (61). Therefore, rapid image acquisitions are necessary to observe this phenomenon, and the scans are typically performed over about 8 minutes to observe the enhancement and washout of lesions. Time-intensity curves may be calculated over enhancing regions of interest. Malignancies usually exhibit the cancer curve (62), reflecting the rapid peak at 90 seconds to 2 minutes and then immediate washout. Benign lesions tend to continually enhance or to plateau. The sensitivity of breast MRI for detection of invasive breast cancer is high, ranging from 88% to 99%, but the specificity is lower (28%–80%) (63,64,65,66,67,68). Even in cases of DCIS, early contrast enhancement has been demonstrated, and tumor angiogenesis has been found in the stroma in these cases (69).
The pattern of enhancement and shape of masses on MRI suggest their possible etiologies. On T2-weighted images, certain benign lesions are high in signal, particularly cysts, lymph nodes, and myomatous fibroadenomas (70). The vast majority of breast cancers are not high in signal on T2-weighted images, although occasionally necrotic tumors or mucinous carcinomas (71) may be bright on T2. The shape of lesions on MRI can be described as round, oval, lobulated, or irregular; the margins are smooth, irregular, or spiculated (70); and these findings parallel the mammographic findings.
Patterns of enhancement are homogeneous or heterogeneous. Findings that are suspicious for malignancy include heterogeneous enhancement, rim enhancement, enhancing
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septations, or central enhancement (70). Liberman et al. (72) found that MRI features with the highest positive predictive value of malignancy were a spiculated margin (80% cancers), rim enhancement (40% cancers), and an irregular shape (38% cancers). Dark internal septations are characteristic of fibroadenomas. Inflamed cysts and fat necrosis may show thin rims of enhancement. Nonmass patterns of enhancement may be linear or segmental, which suggest a ductal orientation, and are worrisome for DCIS. Regional or diffuse enhancement patterns are more often benign, but it is important to look for symmetry when this finding is observed. When linear or segmental enhancement has a clumped or irregular pattern, it is particularly suspicious for DCIS (70) (Fig. 17.41). Orel et al. (73) described MRI findings of DCIS and found that 77% of cases showed ductal enhancement and regional enhancement or a peripherally enhancing mass.
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Figure 17.36 HISTORY: Patient with a history of silicone implants with a question of rupture. IMAGING: Ultrasound over the left axillary tail shows signs of extracapsular rupture. There is an echogenic focus anterior to the edge of the implant with associated dense acoustic shadowing, the snowstorm appearance. IMPRESSION: Extracapsular silicone implant rupture. |
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Figure 17.37 HISTORY: Postmenopausal patient with newly diagnosed lymphoma and a palpable right breast mass. She had a history of removal of silicone implants for rupture years ago. IMAGING: Right exaggerated CC lateral view (A) show a hyperdense indistinct mass laterally, extending along the chest wall. The density is much greater than that of breast parenchyma, suggesting the possibility of free silicone rather than a breast mass. Ultrasound (B) shows the mass to be associated with very echogenic shadowing, consistent with free silicone. IMPRESSION: Free silicone granulomas. |
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Figure 17.38 HISTORY: Patient with a history of silicone implants with a question of rupture. IMAGING: Sagittal (A) and axial (B) T2-weighted MRI images. Within the silicone is a serpiginous structure that is not connected to the wall. The silicone conforms to the shape of an implant, and there is no extension beyond this shape. The structure within the silicone represents the broken implant wall that is floating within the silicone. The fibrous capsule around the implant is intact and is containing the silicone. IMPRESSION: Intracapsular rupture of the silicone implant (linguine sign). (Case courtesy of Dr. Deanne Lane, Houston, TX. ) |
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Figure 17.39 HISTORY: Patient with a history of augmentation with silicone implants, with a question of rupture. MAMMOGRAPHY: Bilateral axial T2-weighted MRI images (A,B) show low signal serpiginous structures (arrows) within the silicone. A sagittal inversion recovery image of the right breast (C) also shows the linguine sign, which represents the broken implant wall floating within the silicone. The silicone is contained by the fibrous capsule that formed around the implant, so this is not an extracapsular rupture. IMPRESSION: Bilateral intracapsular ruptures of silicone prostheses. (Case courtesy of Dr. Neeti Goel, Harrisburg, PA. ) |
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Figure 17.40 HISTORY: Patient with a history of silicone implants and a question of rupture. IMAGING: Sagittal MRI image of the left breast shows the implant to be slightly irregular in contour. There are multiple rounded “masses” (arrows) extending toward the axillary tail having the same signal intensity as the silicone. The findings are typical of extracapsular rupture. IMPRESSION: Extracapsular rupture of a silicone implant. (Case courtesy of Dr. Patricia Abbitt, Gainesville, FL. ) |
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Figure 17.41 MRI study on a patient who had recently undergone a core biopsy for DCIS in the right breast. Subtraction T1-weighted postcontrast images show an enhancing lesion in the upper aspect of the breast (A,B). Within this area of enhancement is a central susceptibility artifact from the clip that was deployed during the biopsy. A moderate amount of clumped enhancement surrounds the biopsy site, consistent with residual tumor (arrow). HISTOPATHOLOGY: DCIS. (Case courtesy of Dr. Neeti Goel, Harrisburg, PA. ) |
Magnetic Resonance Imaging for the Assessment of Local Extent of Carcinoma
As more and more women undergo breast conservation therapy, it is critical that careful preoperative assessment of the patient be performed to assure that she is a good candidate for this treatment. MRI is particularly helpful for assessing the size, number, and location of breast cancers. MRI has been demonstrated to more accurately assess tumor size than mammography (74,75,76,77,78). Weinstein et al. (79) found that MRI imaging showed more extensive tumor
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than conventional imaging and affected the clinical management in 50% of patients with invasive lobular carcinoma.
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Figure 17.42 HISTORY: Patient with biopsy-proven cancer in the left upper-outer quadrant, for assessment of extent of disease. IMAGING: T1-weighted sequence postcontrast, subtraction sagittal image shows a large rim-enhancing irregular mass in the upper aspect of the breast, corresponding to the cancer. Extending anterior to the mass is clumped linear enhancement that is suggestive of intraductal extension of tumor. In addition, there is a separate area of linear enhancement in the subareolar region, likely representing another focus of DCIS. Biopsy of this region was performed as well. HISTOPATHOLOGY: Invasive ductal carcinoma, DCIS, multicentric. (Case courtesy of Dr. Deanne Lane, Houston, TX. ) |
Additional foci of tumor representing either multifocal or multicentric disease may be demonstrated on MRI, when only the index lesion is evident on mammography (80,81,82) (Figs. 17.42 and 17.43). In the patient with multicentric carcinoma, mastectomy is indicated, so the preoperative diagnosis of multiple cancers greatly affects patient management. Orel et al. (83) found that as a result of the increased sensitivity of MRI compared with mammography, clinical staging and treatment were altered in 11% of patients with breast cancer.
Boetes et al. (75)—in a study of 60 women with 61 cancers that were evaluated with mammography, ultrasound, and MRI before mastectomy—found that MRI was the most accurate method to assess the size and number of malignancies. Liberman et al. (84) found additional sites of ipsilateral cancer with MRI in 27% of women with percutaneous proven breast cancer. The yield was highest in women with family history of breast cancer or an infiltrating lobular histology.
In a study of 67 patients with dense breasts and cancers, MRI depicted 100% of the multifocal or multicentric cancers (20 patients), whereas mammography found 35% and ultrasound depicted 31% of the additional malignancies (85). In a study comparing mammography, ultrasound, and MRI in patients with known breast cancers, Berg et al. (86) found that mammography had a sensitivity of 100% for additional foci in fatty breasts, but the sensitivity was 45% in dense breasts. The sensitivity of mammography for the detection of invasive ductal carcinoma was 89%; invasive lobular carcinoma, 34%; and DCIS, 55%. MRI sensitivities for the same lesions were 95%, 96%, and 89%, respectively (86). Sardanelli et al. (87) also found MRI to be significantly more sensitive than mammography in the detection of multiple malignant foci in dense breasts, but there was not a significant difference in fatty breasts.
The depiction of additional foci in the same breast or the contralateral breast should prompt biopsy before any change in the definitive treatment plan (Fig. 17.44). Because of the limited specificity of MRI, additional enhancing lesions may represent other foci of cancers, but in most cases, they are benign. Liberman (88) found that biopsies performed because of MRI-depicted contralateral lesions were benign in 80% of patients. Contralateral cancers have been identified on MRI in 2% to 9% of cases (89,90). Therefore, histologic sampling of additional findings on preoperative breast MRI should be performed before treatment decision making is affected (91).
Postoperative MRI assessment of the patient with newly diagnosed breast cancer may also yield important information that affects the final surgical management and treatment. Normal finding after lumpectomy is a seroma, which has a smooth, thin rim of enhancement. Positive surgical margins might suggest the presence of residual disease and prompt imaging with MRI. The observation of linear clumped enhancement around the lumpectomy site suggests the presence of residual DCIS. MRI can confirm the presence of residual carcinoma as well as possible other foci elsewhere in the breast. Orel et al. (80) evaluated MRI for the assessment of residual tumor and found that MRI had a positive predictive value of 82% and a negative predictive value of 61% for assessment of residual tumor.
Assessment of Recurrent Carcinoma
In the early postoperative period, the lumpectomy site may be visible on subtraction images as having thin rimlike enhancement. This pattern of enhancement may persist until 18 months after surgery. From this point on, enhancement at the lumpectomy site should be viewed with suspicion for malignancy.
In patients who have been treated with breast conservation therapy, the sensitivity of mammography for the
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detection of local possible recurrence has been reported to be 55% to 70% (92,93). MRI is useful, particularly after the first 18 months, to detect local recurrence (94,95). In the first 12 months after treatment, fat necrosis at the lumpectomy site is associated with poorly defined enhancement patterns that may be confused with tumor.
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Figure 17.43 HISTORY: A 44-year-old woman with a strong family history of breast cancer and with newly diagnosed breast cancer, for assessment of extent of disease. MRI: T1-weighted subtraction postcontrast images show a rim-enhancing mass in the right breast (A,B). Adjacent to this lesion is some clumped enhancement suggestive of the possibility of intraductal extension. Multiple small enhancing foci were seen in the opposite breast. A time-intensity curve (C) over the larger mass shows the typical cancer curve of rapid wash in and rapid wash out of contrast. IMPRESSION: Possible intraductal extension of tumor. HISTOPATHOLOGY: Invasive ductal carcinoma, DCIS. |
Findings on mammography that might suggest the possibility of recurrence are an increase in size or density of the scar or an increase in skin thickness. Because of the overall edema of the breast and the difficulty in compressing some irradiated breasts, these findings may be subtle. With recurrence, MRI demonstrates enhancement at the region of the scar or elsewhere in the breast (Fig. 17.45) and may show diffuse skin enhancement when an inflammatory recurrence is present.
Neoadjuvant Chemotherapy
In patients with locally advanced breast cancer or in patients with large tumors relative to the breast size, neoadjuvant chemotherapy may be given to reduce the tumor burden before surgery. In patients with large tumors (>5 cm), the use of neoadjuvant chemotherapy has been shown to reduce the need for mastectomies and to increase the rate of lumpectomies by 175% (96).
In addition to trying to reduce the tumor burden with neoadjuvant chemotherapy, one may be able to determine potential outcome. Those tumors that show a marked response to neoadjuvant therapy may be those with an overall better outcome (91). The lack of response to the chemotherapy usually prompts surgery rather than completing the preoperative chemotherapy regimen.
MRI has been found to be better than mammography and ultrasound in the assessment of the size of tumor (91). However, overestimates of residual tumor by MRI range from 6% to 52% (97,98), and underestimates range from 10% to 23% (97,98). Underestimation of disease has been found to be greater in invasive lobular carcinoma and has been reported to occur in 78% of cases (99).
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Figure 17.44 HISTORY: Patient with biopsy-proven left breast cancer, referred to assess for extent of disease. MAMMOGRAPHY: Left (A) and right (B) sagittal subtraction postcontrast imaging. There is a lobular enhancing mass that has heterogeneous enhancement located in the left subareolar area (A). This lesion is highly suspicious for malignancy, and this corresponded to the biopsied cancer. Multiple small enhancing foci are noted in the same breast. An enlarged enhancing node is also noted in the inferior axillary region (arrow) on the left, suspicious for metastatic involvement with tumor. On the right (B), there is linear, ductal enhancement in the subareolar area, extending back toward a small lobulated enhancing mass in the inferior pole of the breast. IMPRESSION: Multicentric carcinoma left breast with positive axillary adenopathy; DCIS and invasive cancer right breast. HISTOPATHOLOGY: Left invasive ductal carcinoma, multicentric; mucinous carcinoma, right breast. (Case courtesy of Dr. Deanne Lane, Houston, TX. ) |
The Positive Axillary Node
The vast majority of patients who have metastatic breast cancer in the ipsilateral axillary nodes have a clinical or mammographic presentation of the cancer within the breast. Occasionally, though, the primary cancer may be clinically and mammographically occult, yet the patient presents with an enlarged axillary node that is positive for adenocarcinoma on biopsy. MRI can be valuable in these circumstances in identifying the primary breast cancer.
The treatment of patients with a positive node and no primary cancer identified in the breast has been controversial, yet in most cases, mastectomy has been performed. With MRI detection of the primary cancer, the patient may be able to undergo breast conservation therapy. In addition, the histology and the cellular features of the tumor are important to treatment planning (74,100). Obdeijn et al. (101) studied the role of MRI in 31 women with metastatic carcinoma in axillary nodes from an unknown primary site and with negative mammography and physical exam. MRI revealed the primary breast cancer in 40% of the patients who had no prior history of malignancy.
Other Clinical Situations
MRI plays a role in several other clinically and mammographically equivocal situations. In patients with suspicious nipple discharge and negative imaging, MRI may identify the source of the discharge. A papilloma may be identified as an intermediate signal-intensity mass within a dilated duct on T2-weighted images and is a homogeneously enhancing mass after contrast (74). Small peripheral papillomas are round enhancing masses, and DCIS is often seen as linear or clumped enhancement. Orel et al. (102) suggested the role of MRI imaging to identify benign
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and malignant causes of discharge and to potentially serve as an alternative to galactography.
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Figure 17.45 HISTORY: A 52-year-old patient with a history of left breast cancer treated with lumpectomy and radiotherapy 7 years previously. She reports increased heaviness of the treated breast. IMAGING: Mammography showed postoperative changes with questionable increase in skin thickness on the left. MRI was performed and shows signs of recurrence on the subtraction postcontrast T1-weighted axial image. There are three enhancing lobular masses in the left breast, suspicious for recurrence. The lesions were identified on ultrasound. Biopsy was performed using ultrasound guidance. IMPRESSION: Enhancing masses in the treated breast, most suggestive of recurrent carcinoma. HISTOPATHOLOGY: Invasive lobular carcinoma, multicentric, recurrent. |
Ductal lavage is sometimes performed in high-risk women to search for atypical cells. This procedure involves flushing fluid into the ducts and collecting the expressed fluid for cytologic analysis. In patients with positive or suspicious ductal lavage findings and negative imaging, MRI may be used to search for a potential malignancy (51).
Equivocal mammographic findings, such as focal asymmetries that do not have an associated clinical or sonographic finding, may occasionally be evaluated with MRI. In these situations, a negative MRI may prompt follow-up rather than biopsy for a density that is of low suspicion, whereas a positive MRI leads to biopsy (74).
The Role of Magnetic Resonance Imaging in Screening for Breast Cancer
The limitations of screening mammography are greater in women with dense parenchyma that may obscure underlying noncalcified masses. Younger women tend to have denser breasts, but this is not necessarily so. Breast density depends on a number of factors, including body habitus, weight, and parity, as well as parenchymal factors. The risk of breast cancer is less in younger women, and the risk of the disease increases with age.
Young women who are at high risk of developing breast cancer or those women who are at higher risk and who have dense breasts are those who may potentially benefit most from screening MRI. MRI has a high sensitivity for the detection of invasive cancers greater than 3 mm in size, and parenchymal density does not limit its sensitivity. Therefore, if screening MRI is to be used, the populations it may best serve are those women who are at high risk for breast cancer and those with dense parenchyma. Several small studies have reported on screening MRI-detected breast cancers in high-risk women (103,104,105,106). Morris et al. (103) found 14/367 high-risk women (4%) to have MRI-detected, mammographically occult breast cancers. Kriege et al. (107) from the Netherlands reported on screening 1,909 high-risk women who had proven genetic mutations or positive family history. Clinical examination, mammography, ultrasound, and MRI were used to screen the women, and 45 cancers were found, 22 of which were seen on MRI only.
A number of potential problems exist with MRI screening, including the following (108): the ability to tolerate the procedure or be a candidate for MRI, contrast reaction, cost of the procedure, high number of false positives, determination of protocols for “probably benign” MRI-detected lesions, and accessibility to a breast MRI facility. The potential for MRI to detect cancers in certain select populations is great.
Because of many of the above cited disadvantages, screening MRI will not likely be a replacement for mammography or a generally used study. MRI, like ultrasound, plays an important role in the comprehensive evaluation of women with breast abnormalities, many of which are detected on mammography. The gold standard for early detection of breast cancer and the tool proven to reduce mortality for this disease remains mammography.
References
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