PERSPECTIVE, PATTERNS OF SPREAD, AND PATHOLOGY
The use of Ohngren's plane provides the malignant gradient of the maxillary antrum, dividing the sinus into an anterior-inferior compartment and a posterior-superior pocket.
PERSPECTIVE AND PATTERNS OF SPREAD
Tumors arising in the paranasal sinuses can be both very destructive and deforming. Fortunately, they are uncommon. Cancers of the maxillary antrum and ethmoid are among those more frequently encountered. The unique anatomic feature at these sites is the direct juxtaposition of the mucous membrane with very thin bony walls. Unfortunately, the manifestations of localized cancers are similar to sinusitis. Consequently, most cancers masquerade as infections and go unrecognized. It is no surprise, therefore, that the first detectable clinical signs of cancer are of advanced spread, most often owing to invasion through bony walls (Fig. 3.2). To the astute clinician, a persistent unilateral sinusitis may be a clue to an underlying cancer.
As for most sites, the cancer infiltrates the surrounding structures, which depends on its site of origin. Pathways of least resistance are at the foramina or where the bone is thinnest and are manifested by displaying a number of typical signs. The infrastructure of the maxillary sinus is the most common site of cancer origin, and the medial wall is easy to penetrate because of the normal ostia. Bloody nasal discharge appears before erosion of this paper-thin wall. As the mass extends medially into the nose, nasal obstruction can occur. The floor of the maxillary sinus is in close contact with molar dental roots and their nerves. Consequently, as the bone is destroyed with inferior spread, there is filling of the gingivobuccal gutter, loosening of teeth, and finally an ulcerating lesion and loss of the alveolar bone with extension into the hard palate (Fig. 3.2A,B).
Cancers of the suprastructure usually occur at the summit of the sinusoidal pyramid. They extend into the malar bone and the outer half of the floor of the orbit into the temporal fossa. The skin of the cheek rapidly expands, often as a result of infection, and the zygomatic arch can be destroyed. The eye can be displaced and become proptotic when there is superior invasion. A posterior location and spread of cancer is less common, but in advanced states, the tumor, particularly when it is aggressive, can explode the sinus cavity and move in all directions via the associated infection. Under these circumstances, the cancer invades the pterygoid plates and muscles, leading to trismus (Fig. 3.2B). Patterns of Spread are presented as a cancer crab that can invade in six basic directions Superior-Inferior, Medial-Lateral, Anterior-Posterior (SIMLAP) of adjacent anatomic sites (Fig. 3.2; Table 3.2).
Figure 3.1 | Sinonasal inverted papilloma. Epithelial nests are growing downward (inverted) into the submucosa. They are composed of a uniform cellular proliferation, which displays an inflammatory cell infiltrate and scattered microcysts.
Figure 3.2 | Patterns of spread. A. Coronal. Patterns of Spread into orbit superiorly, check laterally, and palate inferiorly. B. Sagittal. Pattern of Spread into palate inferiorly and pterygoid fossa posteriorly. The primary cancer (maxillary sinus antrum) invades in various directions, which are color-coded vectors (arrows) representing stage of progression. Tis, yellow; T1, green; T2, blue; T3, purple; T4a, red; and T4b, black. The concept of visualizing patterns of spread to appreciate the surrounding anatomy is well demonstrated by the six directional pattern, i.e. SIMLAP Table 3.2.
PATHOLOGY
Papillomas of the nasal cavities and paranasal sinuses show inversion patterns of surface epithelia that are in the underlying stroma (Figure 3.1). Often HPV have been associated. In a small percentage (≤5%) become squamous cell cancers. Most maxillary antral cancers are squamous cell cancers (Table 3.1). Ethmoid cancers can be either squamous cell or adenocarcinomas. In contrast, tumors of the nose are highly varied, although again, they are most often squamous cell cancers.
TNM STAGING CRITERIA
TNM STAGING CRITERIA
The TNM criteria for the maxillary antrum was initiated in the first edition of the American Joint Committee on Cancer/International Union Against Cancer (AJCC/UICC) and are based on patterns of spread into subsites rather than size. The subsite criteria were introduced with the fourth edition of the AJCC/UICC (1992) and are based on patterns of spread rather than size (Fig. 3.3). The use of Ohngren's plane provides the malignant gradient of the maxillary antrum, dividing the sinus into an anterior-inferior compartment and a posterior-superior pocket. With massive invasion, cancer of the maxillary sinus can invade other paranasal sinuses, enter into the cranial fossa, and even reach the lateral pterygoid space. Lymph node progression from N1, N2, to N3 is the same as most head and neck cancer sites and is based on size, laterality, and number of nodes.
SUMMARY OF CHANGES SEVENTH EDITION AJCC
The TNM stages according to the 7th Edition of AJCC are illustrated in color code of advancement (Fig. 3.3). T4 lesions have been divided into T4a (moderately advanced local disease) and T4b (very advanced local disease), leading to the stratification of Stage IV into Stage IVA (moderately advanced local/regional disease), Stage IVB (very advanced local/regional disease), and Stage IVC (distant metastatic disease). The TNM Staging Matrix is color coded for identification of Stage Group once T and N stages are determined (Table 3.3).
MAXILLARY SINUS ANTRUM
Figure 3.3 | TNM stage grouping. Maxillary antrum cancers invade through their paper-thin bone walls in all six directions. Vertical presentations of stage groupings, which follow the same color code for cancer stage advancement, are organized in horizontal lanes. Stage 0, yellow; I, green; II, blue; III, purple; IVA, red; IVB and IVC, black. Definitions of TN on left and stage grouping on right.
T-ONCOANATOMY
ORIENTATION OF THREE-PLANAR ONCOANATOMY
For the maxillary antrum the anatomic isocenter is at the level of the clivus. The anterior surface bullet is at the level of or slightly inferior to the bridge of the nose to the right and left of the midline (Fig. 3.4A). Centered inferior to the pupil of the eye (Fig 3.4B), the lateral bullet is at the level of the external auditory canal and inferior to a line connecting the lateral can-thus of the eye and the external auditory canal.
T-oncoanatomy
To appreciate the manifestation of cancer of the paranasal sinus, a thorough knowledge of the three-dimensional aspects of paranasal sinus anatomy is essential. The eight major sinuses in the face and skull are in direct continuity. The four paired sinuses are the maxillary, the ethmoid, frontal sinuses, and the sphenoid. Although the sphenoid appears as a single midline sinus, it is also a paired sinus. A three-dimensional reconstruction, focusing on bony anatomy, allows for an understanding of the interrelationships. The anatomy may be divided by drawing three parallel lines across the frontal view of the skull, one line passing above and another below the orbits, the third passing through the floor of the antra or hard palate. The two vertical lines separate the ethmoid and nasal fossa from the maxillary antra. The nasal septum separates the ethmoid and nasal fossa into the right and left sides.
• Coronal plane (Fig. 3.5A): In a comparison of anteroposterior and lateral projections or coronal and sagittal sections, three important planes become evident: (i) The floor of the anterior fossa of the skull (in the roof of the nasal cavity and ethmoid); (ii) The hard palate, in the floor of the maxillary antra; and (iii) An imaginary plane below the orbits that divides the paranasal sinuses into a suprastructure and an infrastructure. The suprastructure contains the ethmoids, anterior to which is the apex of the nasal cavity and cribriform (olfactory region). The sphenoid sinus is posterior, the orbits are medial, and the nasal fossa and turbinates are inferior to the suprastructure. The infrastructure contains the maxillary antra and the major portion of the nasal cavity or vestibule. These planes are helpful in relating the external anatomy of physical diagnosis to the radiographic anatomy.
• Sagittal plane (Fig. 3.5B): The relationship of the teeth in the superior alveolus determines which teeth are affected as tumor invasion of the floor occurs. First, the second premolar or bicuspid and the first and second molars are in the floor itself and become loosened. The upper canine may become involved when there is more anterior invasion. Rarely, however, are the incisors affected. The third molar can be loosened when there is posterior extension. The ethmoid sinuses are the central paranasal space in the supra-structure with communication to the frontal sphenoid sinuses and the nasal cavity. The ethmoid bone also constitutes the cribriform plate and the superior and medial concha. The important nerves in its walls are (i) the anterior ethmoidal branch of the ophthalmic division of the cranial nerve V (anterior at the junction with the frontal sinus); (ii) the olfactory nerve and bulb in and above the cribriform plate; and (iii) the nasociliary nerve inside the orbit that branches into the posterior and anterior ethmoidal nerves, infratrochlear, and the internal nasal branches.
• Transverse plane (Fig. 3.5C): The maxillary antrum is the essential paranasal sinus to study in the infrastructure. It is pyramidal with its apex at the malar arch and base at the nasal cavity. It projects as a triangulated space from virtually every view. The bony walls consist of the maxillary bone in its entirety laterally, anteriorly, and inferiorly. The medial wall is constituted inferiorly by the concha and palatine bone, superiorly and laterally by the zygomatic bone, and posteriorly by the pterygoid plates of the sphenoid. The important nerves to identify in these walls are those in the infraorbital branch of the maxillary division of cranial nerve V through the canal in the perpendicular plate of the palatine posteriorly. The posterior aspect and its relationship to the pterygoid plates and muscle with its access to major vessels and retropharyngeal nodes should be noted.
Figure 3.4 | Orientation of three-planar T-oncoanatomy. The anatomic isocenter is at the axial level of the clivus. A. Coronal. B. Sagittal.
Figure 3.5 | T-oncoanatomy. The Color Code for the anatomic sites correlates with the color code for the stage group (Fig. 3.3) and patterns of spread (Fig. 3.2) and SIMLAP table (Table 3.2). Connecting the dots in similar colors will provide an appreciation for the 3D Oncoanatomy.
N-ONCOANATOMY AND M-ONCOANATOMY
N-ONCOANATOMY
Lymphatic involvement occurs late, despite extensive disease. The submaxillary node is usually the first (often the only) node invaded and it is the sentinel node (Fig. 3.6A). The major lymphatic drainage of the maxillary antrum is through the lateral and inferior collecting trunks to the first station submaxillary, parotid, and jugulodigastric nodes, and via the superoposterior trunk to the retropharyngeal and deep cervical nodes (Table 3.4).
M-ONCOANATOMY
The pterygoid plexus of veins drains the maxillary sinuses into the internal jugular vein, the subclavian, and right heart. The target organ for metastases is the lung (see Fig. 3.6B).
Figure 3.6 | N-oncoanatomy. The red node highlights the sentinel node, which is the submaxillary node. A. Anterior view. B. Lateral view. M-oncoanatomy is determined by the jugular, vein which joins with the subclavian vein to form the superior vena cava on the right, and the innominate vein, which drains into the right side of the heart and then into lung.
Figure 3.7 | M-oncoanatomy. A. Carotid artery with major branches shown. B. Pterygoid plexus of veins drains most of head and neck sites into internal deep jugular. The jugular vein drains into the superior vena cava and then into the right heart, making jung the target organ. Perineural invasion and compression of Ethmoid Cancers is V2 external nasal branch as the cancer invades into Nasal Cavity. The infraorbital perineural invasion occurs with erosion of the lateral wall and floor of the orbit resulting in a round spot of hypoesthesia below the lower eyelid (Fig. 3.7C).
Figure 3.7 C | Cranial Nerve Oncoanatomy.
STAGING WORKUP
RULES OF CLASSIFICATION AND STAGING
Clinical Staging and Imaging
Inspection and palpation of paranasal sinuses is limited in early localized stages. For ethmoid cancers, orbital invasion may displace the globe and trap the anterior ethmoid branch of cranial nerve V1, leading to altered sensation in the upper lip. Maxillary antral cancers when advanced fill the gingival buccal gutter, loosen molar teeth, and invade the cheek and hard palate. Infection and inflammatory sinusitis obscures cancers. Both magnetic resonance imaging (MRI) and computed tomography enhancement (CTe) are recommended to distinguish tumor from fluid. CTe is best for determining bone erosion of the paper-thin lamina bones of sinus walls. (Fig. 3.8). Imaging is essential for evaluation of retropharyngeal nodes (see Table 3.5).
Pathologic Staging
The gross specimen should be evaluated for margins. Unresected gross residual tumor must be included and marked with clips. All resected lymph node specimens should describe size, number, and level of involved nodes and whether there is extracapsular spread. Specimens after radiation, chemotherapy, or both need to be so noted, but specimen shrinkages may occur up to 30% after resection itself. Designations pT and pN should be used after histopathologic evaluation. Perineural invasion deserves special notation.
Oncoimaging Annotations
• MRI and CT play complementary roles in the assessment and staging process for these tumors.
• Most minor salivary gland neoplasms arise from the palate and secondarily extend into the nasal cavity and paranasal sinuses.
• MRI is best at detecting tumor extension outside the sinonasal cavity. CT is most sensitive in assessing anatomy and bone invasion with these tumors. The hallmark of sinonasal malignancy is bone destruction, seen in approximately 80% of all CT scans in these patients.
• Enlargement of the infraorbital foramen on CT occurs with perineural invasion of the infraorbital nerve, a branch of cranial nerve V2.
• MRI aids in separating complex sinonasal secretions/infections from tumor. Combined T1- and T2-weighted, contrast medium-enhanced images are needed for this evaluation.
• Orbital extension is manifest on CT and MRI by bone erosion and changes in the orbital fat. Unfortunately, the absence of orbital fat abnormality does not exclude invasion. MRI tends to underestimate orbital invasion.
• Sinonasal bony sclerosis caused by tumor is rare; its presence is normally related to coexistent chronic inflammatory changes.
• Carotid encasement is a relative contraindication to surgery and is suggested by MRI when the internal carotid artery is surrounded by more than 270 degrees with tumor.
• Mature scar after treatment can usually be distinguished from tumor by the absence of a mass effect, a hypodense appearance on T2-weighted images, and the lack of contrast medium enhancement.
PROGNOSIS AND CANCER SURVIVAL
CANCER STATISTICS AND SURVIVAL
Generally, cancers of the oral cavity, pharynx, and the upper digestive passage account for 36,540 new cases. In addition, cancer of the larynx affects another 12,720 patients and thyroid cancers, 44,670. Approximately 25% of head and neck cancer patients die annually, often owing to other causes. Thyroid cancer is the exception for long-term survival, with only 1,500 deaths (5%). The improvement in oral cavity and pharyngeal tumors from 1950 to 2000 was modest at 14% and matches larynx at 15%. A multidisciplinary approach is vital and both normal tissue conservation and reconstruction techniques have added greatly to quality of life. Unfortunately, this patient population comprises ethanol and nicotine abusers and it is difficult to change these habits. Persistence of smoking and drinking contributes to their demise, often from second malignant tumors in adjacent sites.
Specifically, paranasal sinus cancers are detected late due to being mistaken for sinusitis. Both ethmoid and maxillary sinus cancers overall survival is below 50% for 5-year survival rates. However, if detected early, stage I/II 5 year survival is 60% (Figure 3.9).
Figure 3.8 | MRI of (axial) view.
Figure 3.9 | Five-year survival rates by stage at diagnosis. (Data from Edge SB, Byrd DR, and Compton CC, et al, AJCC Cancer Staging Manual, 7th edition. New York, Springer, 2010.)