PERSPECTIVE, PATTERNS OF SPREAD, AND PATHOLOGY
The designation of Pancoast refers to a tumor arising in the apex of lung in the neck that involves the brachial plexus and the stellate ganglion.
PERSPECTIVE AND PATTERNS OF SPREAD
The apex of the lung is in the base of the neck. The anatomy between the neck and thorax is a transitional zone because the thoracic vertebrae T1 and T2 are in the neck above the suprasternal notch. The “Pancoast” tumor refers to a symptom complex or syndrome caused by a tumor arising in the superior sulcus of the lung, which is juxtaposed with and therefore involves the inferior branches of the brachial plexus (C8 and T1) and traps the stellate ganglion of the cervical sympathetic chain which resides on the transverse process of T1 resulting in Horner's syndrome (shoulder and arm pain with ptosis, miosis, unilateral flushing, and anhidrosis).
The apical location and superior sulcus cancers in the lung apex do not present in a typical fashion with a productive cough, hemoptysis, or blood-streaked sputum, but as a progressive neuralgia with referred shoulder pain to the ulnar side of the arm. Horner's syndrome is usually subtle in onset and misleading; symptoms are related to a neurologic syndrome rather than a neoplastic process in lung. The intimate anatomic relationship of lung apex to brachial plexus and the stellate ganglion explains the onset of symptoms once the cancer spread is into the soft tissues of the neck (Fig. 13.2 and Table 13.2).
An unusual syndrome can occur with lateral invasion into the subclavian artery. Entrapment of the right recurrent laryngeal nerve could result in right vocal cord paresis and a thoracic inlet syndrome (TIS). TIS can be elicited by holding the patient's wrist with a finger on the radial artery pulse. As the arm is elevated, the pulse disappears due to tumor compression of the subclavian artery.
PATHOLOGY
A variety of histopathologic tumor types are possible (Table 13.1). The cells of tumor origin are in the terminal bronchioles, ranging from ciliated simple columnar to simple cuboidal cells. Cancers vary from 25% to 40% squamous cell, 25% to 60% adenocarcinoma (Fig. 13.1A and 13.1B), 5% to 15% large cell, and 2% to 5% small cell.
Figure 13.1 | Adenocarcinoma of the lung. A: A peripheral tumor of the right upper lobe has an irregular border and a tan or gray cut surface and causes puckering of the overlying pleura. B. A tumor grows in the pattern of solid adenocarcinoma with mucin formation. Several intracytoplasmic mucin droplets stain positively with the mucicarmine stain.
Figure 13.2 | Patterns of spread. The primary cancer (Pancoast) invades in various directions, which are color-coded vectors (arrows) representing stage of progression: Tis, yellow; T1, green; T2, blue; T3, purple; T4, red. The concept of visualizing patterns of spread to appreciate the surrounding anatomy is well demonstrated by the six-directional pattern i.e. SIMLAP Table 13.2.
TNM STAGING CRITERIA
TNM STAGING CRITERIA
The designation of Pancoast tumors refers to the symptom complex or syndrome caused by a tumor arising in the superior sulcus of the lung that involves the inferior branches of the brachial plexus (C8 or T1) and the sympathetic nerve trunks, including the stellate ganglion. Some superior sulcus tumors are more anteriorly located and may cause fewer neurologic symptoms even when they are very locally advanced and encase the subclavian vessels. If there is evidence of invasion of the vertebral body or spinal canal, encasement of the subclavian vessels or unequivocal involvement of the superior branches of the brachial plexus (C8 or above), then the tumor is classified as T4. If no criteria for T4 disease pertain, the tumor is classified as T3.
Although the usual TNM criteria apply, because of the anatomic location, some exceptional findings need to be appreciated. T1 and T2 lesions less than 3 cm or greater than 3 cm are difficult to detect on routine chest films due to overlay of ribs and clavicle, which obscures small opacities in the lung. Diagnosis is most often made when the cancer reaches stage T3 because of persistent shoulder pain, which leads to discovery of chest wall invasion and posterior rib erosion on film before extensive perineural invasion, while resection is possible. Patterns of neurologic involvement vary according to which surface the cancer invades first. Thus, with superior invasion of the brachial plexus trunks of TI, C8, and C7, ribs are eroded laterally, vertebrae are invaded posteriorly, and major vessels (subclavian artery and vein) are involved anteriorly at the thoracic inlet. The difference between stages T3 and T4 is that the latter can be due to invasion of the vertebral body and unequivocal involvement of spinal cord at C8 with disastrous paraplegia or complete cord transection and quadriplegia before death. Invasion of the chest wall, pleura, and ribs imply resection is possible and therefore is considered to be T3.
• This staging system is now recommended for the classification of both non–small cell and small cell lung carcinomas and for carcinoid tumors of the lung (Fig. 13.3).
• The T classifications have been redefined:
• T1 has been subclassified into T1a (≤2 cm in size) and T1b (>2–3 cm in size)
• T2 has been subclassified into T2a (>3–5 cm in size) and T2b (>5–7 cm in size)
• T2(>7 cm in size) has been reclassified as T3
• Multiple tumor nodules in the same lobe have been reclassified from T4 to T3
• Multiple tumor nodules in the same lung but a different lobe have been reclassified from M1 to T4
• No changes have been made to the N classification. However, a new international lymph node map defining the anatomical boundaries for lymph node stations has been developed.
• The M classifications have been redefined:
• The M1 has been subdivided into M1a and M1b
• Malignant pleural and pericardial effusions have been reclassified from T4 to M1a
• Separate tumor nodules in the contralateral lung are considered M1a
• M1b designates distant metastases
Because of the magnitude of the T-category changes with shifts in both directions, that is both downstaging and upstaging, it is important to review the stage groupings of the sixth and seventh editions. The TNM Staging Matrix is color coded for identification of Stage Group once T or N stages are determined (Table 13.3).
PANCOAST CANCER
Figure 13.3 | TNM staging diagram. Pancoast cancers originate in cupula of lungs and are located in the base of the neck and spread into supraclavicular and cervical nodes. 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; IIIA, purple; IIIB, red; and metastatic stage IV, black. Definitions of TN are on the left and stage groupings are on the right.
T-ONCOANATOMY
ORIENTATION OF THREE-PLANAR ONCOANATOMY
The isocenter of the pulmonary apex is in the neck, around which the three-planar anatomy is presented, especially as it relates to the brachial plexus and sympathetic chain of cervical ganglion. It is important to note that T1 and T2 are above the thoracic inlet and form a transitional zone between the neck and the chest, that is, the thoracic inlet (Fig. 13.4).
T-oncoanatomy
Designated at the T1-2 level, the Pancoast tumor is fitting to introduce lung cancer as a disease with many different presentations, which masquerade the underlying cancer. The misleading signs and symptoms in the presentation of a Pancoast cancer stem from the anatomic location of the superior sulcus of the lung in the neck and not the thorax. Grave signs are direct vertebral invasion, which can result in spinal cord encroachment and transection leading to paraplegia or entrapment of major vessels, namely, the subclavian artery and vein. The coronal and sagittal views are more revealing of the critical anatomy of the superior sulcus (Fig. 13.5).
• Coronal: The juxtaposition of the brachial plexus superior and posterior to the lung apex is readily seen.
• Sagittal: The brachial plexus and subclavian artery are appreciated as to their proximity to the lung apex posteriorly and anteriorly, respectively.
• Transverse: The medial location of the stellate ganglion anterior to the transverse process of T1. The spinal cord is accessible once the vertebral foramen are eroded. This is a striking view of the roof of the thoracic cavity from a diaphragmatic vantage point. The thoracic inlet is the zone that allows cancers to trap nerves, arteries, and veins and compress them against boney ribs and vertebrae; they are between the proverbial rock and a hard place.
Figure 13.4 | Orientation of T-oncoanatomy. The anatomic isocenter is at the T1-2 level at the base of the neck in its transition to the thoracic inlet. A. Coronal. B. Sagittal.
Figure 13.5 | T-oncoanatomy. Connecting the dots: Structures are color coded for cancer stage progression. The color code for the anatomic sites correlates with the color code for the T stage group (Fig. 13.3) and patterns of spread (Fig. 13.2) and SIMLAP tables (Table 13.2). Connecting the dots in similar colors will provide an appreciation for the 3D Oncoanatomy.
N-ONCOANATOMY AND M-ONCOANATOMY
N-ONCOANATOMY
Once the pleural surface is invaded, the cancer drains into scalene or cervical nodes by way of the superior intercostal lymphatics. These lymph nodes often are the ones involved and do not deter the resectability of Pancoast cancers. Intrapulmonary nodes and hilar nodes are possibly, albeit uncommonly, involved (Figs. 13.6 and 13.7; Table 13.4). Ironically, sentinel nodes are metastatic cervical nodes.
REGIONAL LYMPH NODES
The regional lymph nodes extend from the supraclavicular region to the diaphragm. During the past three decades, three different lymph node maps have been used to describe the regional lymph node potentially involved by lung cancers. The first map was endorsed by the Japan Lung Cancer Society. The second map, the Mountain Dresler modification of the American Thoracic Society (MDATS) lymph node map, is used in North America and Europe. The nomenclature for the anatomical locations of lymph nodes differs between these two maps. Recently the International Association for the Study of Lung Cancer (IASLC) proposed a lymph node map (Figure 13.6B) that reconciles the discrepancies between these two previous maps. The IASLC lymph node map is now the recommended means of describing regional lymph node involvement for lung cancers.
There are no evidence-based guidelines regarding the number of lymph nodes to be removed at surgery for adequate staging. However, adequate N staging is generally considered to include sampling or dissection of lymph nodes from stations 2R, 4R, 7, 10R, and 11R for right-sided tumors, and stations 5, 6, 7, 10, L, and 11L for left-sided tumors. Station 9 lymph nodes should also be evaluated for lower lobe tumors. The more peripheral lymph nodes at stations 12-14 are usually evaluated by the pathologist in lobectomy or pneumonectomy specimens but may be separately removed when sublobar resections (e.g., segmentectomy) are performed. There is evidence to support the recommendation that histological examination of hilar and mediastinal lymphenectomy specimen(s) will ordinarily include 6 or more lymph nodes/stations. Three of these nodes/stations should be mediastinal, including the subcarinal nodes and three from N1 nodes/stations.*
M-ONCOANATOMY
Drainage into the subclavian vein, if invaded, then via the superior vena cava and pulmonary artery drain into the lung. Cancer invasion of chest wall drains into intercostal veins, then the azygos vein, and then the superior vena cava, which leads to lung dissemination. Adenocarcinoma dissemination of metastases is the most common lung cancer and is presented as the prototype for metastases into other organs (Fig. 13.7).
*Preceding passage from Edge SB, Byrd DR, and Compton CC, et al. AJCC Cancer Staging Manual, 7th edition. New York, Springer, 2010, pp. 254–255.
Figure 13.6 | A. N-oncoanatomy. Sentinel nodes are scalene and supraclavicular. B. M-oncoanatomy: International Association for Study of Lung Cancer (IASLC). Labels correlate with Table 13.4.
Figure 13.7 | Incidence and distribution of metastases. Adenocarcinoma is the most common lung cancer and is presented as a prototype for lung cancers.
STAGING WORKUP
RULES FOR CLASSIFICATION AND STAGING
Clinical Staging and Imaging
The TNM classification system is primarily for staging non–small cell lung cancers. The most important change dates back to the fourth edition of the American Joint Committee on Cancer (AJCC), where T3 resectable disease was distinguished from T4 unresectable disease. Simultaneously, a greater reliance on more sophisticated imaging has occurred. It is with the sixth edition that computed tomography (CT) and positron emission tomography (PET) are allowed. The imaging modalities for detection and diagnosis apply to staging (Table 13.5). Chest films and CT (preferably spiral) are essential steps in both diagnosis and staging. PET combined with CT helps to overcome motion artifacts. Magnetic resonance imaging (MRI) is useful for mediastinal evaluation. Another advantage of CT over MRI for staging is that it allows for metastatic workup of lung, liver, adrenal and for ribs, and vertebrae, especially for Pancoast cancers (Fig. 13.8).
Pathologic Staging
All pathologic specimens from clinical invasive procedures—bronchoscopy, mediastinoscopy, mediastinotomy, thoracentesis, and thoracoscopy—are applicable to pathologic stage. Thoracotomy and resection of primary and lymph nodes are the mainstay of pathologic staging. Margin status and any residual cancer need to be noted. Preferably, six nodes should be examined.
Surgical resection of primary and regional nodes needs to be carefully evaluated at bronchial stump for adequate margins. All resected nodes should be numbered according to AJCC system and assessed for tumor.
Oncoimaging Annotations
• Chest radiographs seldom detect primary lung cancers in their early stages.
• Spiral CT is useful in high-risk patients to detect nodule and infiltrates.
• PET imaging with18 FDG (fluorodeoxyglucose) appears to be of value in discriminating malignant versus benign nodules.
• CT can detect mediastinal adenopathy, but histologic verification is essential to ascertain if it is malignant.
• Determining N2 versus N3 mediastinal nodes is important; it establishes resectability.
• MRI can be of value in assessing mediastinal invasion, chest wall and rib erosion, and compromised large vein involvement.
• Pancoast cancers are difficult to diagnose on routine chest films.
• CT scan using bone windows detects invasion of ribs and vertebrae.
• MRI is useful for detecting invasion of vertebrae and tumor compressing spinal cord.
PROGNOSIS AND CANCER SURVIVAL
CANCER STATISTICS AND SURVIVAL
Generally, according to Surveillance Epidemiology and End Results data based on 16,000 patients, the relative 5-year survival is 8% to 10% and 10-year survival 5% to 7%. Surprisingly, there is a small attrition for 5-year survivors with the majority (70%) remaining alive at 10 years. Female gender, good Karnofsky performance status, and cessation of smoking contribute to longer survival.
Specifically, Pancoast cancers were thought to be incurable until a fortuitous long-term survivor (27 years) was reported following preoperative radiation and resection. Nodal status is important because scalene and supraclavicular nodes may be the first involved but are not considered contraindications to surgical resection.
The ability to resect superior sulcus cancers following preoperative radiation was pioneered by Paulson, who posted a 30% 5-year survival rate with a low 3% mortality rate (Fig. 13.9). This has been reproduced by other surgical teams.
PROGNOSIS
The limited number of prognostic factors are listed in Table 13.6.
Prognostic Factors TABLE 13.6
Figure 13.8 | Axial CTs of T1 and T2 level correlate with the T-oncoanatomy transverse section (Figure 13.5C). Oncoimaging with CT is commonly applied to staging lung cancers, often combined with PET to determine true extent of primary cancer and involved lymph nodes. Left. 1, thyroid gland; 2, trachea; 3, internal jugular vein; 4, common carotid artery; 5, esophagus; 6, vertebral artery; 7, clavicle; 8, first rib; 9, scapula. Right. 1, trachea; 2, common carotid artery; 3, internal jugular vein; 4, lung apex; 5, subclavian artery; 6, subclavian vein; 7, clavicle; 8, first rib; 9, scapula (glenoid).
Figure 13.9 | Five-, 10-, and 15-year actuarial survival curves after combined preoperative radiation, followed by en bloc surgical resection (1956–1983) in patients with no lymph nodes involved and including those with nodal involvement. (From Movsas B, Langer CJ, Goldberg M, eds. Controversies in lung cancer. A multidisciplinary approach. New York: Marcel Dekker, 2001).