Chapter 11 Pulmonary Neoplasms
BENIGN NEOPLASMS AND OTHER NONNEOPLASTIC TUMORS
Hamartoma
Amyloid
Characteristics
Amyloid, a waxy pink material that stains with Congo red, has a typical birefringence with polarization microscopy (Box 11-2). It occurs in two major forms: primary and secondary. Lung involvement in primary amyloidosis is estimated to occur in 30% to 90% of cases. Secondary amyloidosis is usually associated with rheumatoid arthritis, suppurative disease such as osteomyelitis, and malignant neoplasms. Amyloidosis may also be associated with multiple myeloma. In the thorax, amyloid occurs in two locations. The first is the tracheobronchial tree. Airway amyloidosis is discussed in Chapter 12. Amyloidosis may also involve the lung parenchyma in a nodular form or as a diffuse, infiltrative process.
Pulmonary Pseudotumor
Characteristics
Pulmonary pseudotumors include a number of histologic entities, such as plasma cell granuloma, inflammatory pseudotumor, histiocytoma, xanthoma, and mast cell granuloma (Box 11-3). The cause of pulmonary pseudotumors is unknown, although they were thought to represent a localized form of organizing pneumonia in patients with subclinical infection. Plasma cell granuloma is discussed more extensively in Chapter 9. Pulmonary pseudotumors occur slightly more frequently in males than in females over a wide age range. Patients are often asymptomatic, and antecedent infection can be documented in less than one fifth of cases.
LUNG CANCER
Clinical Features
Certain occupational agents may increase the risk of lung cancer, and they are listed in Box 11-4. The most important of these is asbestos. A combination of asbestos exposure and cigarette smoking is multiplicative and results in a marked increased risk of lung cancer, particularly if asbestosis is present in the parenchyma of the lungs. Most of the concomitant lung diseases associated with bronchogenic carcinoma reflect the presence of fibrosis in the lungs (Box 11-5), including any cause of end-stage lung disease, such as idiopathic pulmonary fibrosis, and localized fibrosing disease, such as tuberculosis.
Radiologic-Pathologic Correlation
Box 11-7 Histologic Classification of Lung Cancer
Modified from the 1999 World Health Organization/International Association for the Study of Lung Cancer Histological Classification of Lung and Pleural Tumours.
Adenocarcinoma
Bronchioloalveolar Carcinoma
Bronchioloalveolar carcinoma is a subtype of adenocarcinoma. It may manifest with one of three distinct radiologic patterns (Box 11-9). The most common is a solitary nodule. The nodules share the same appearance as adenocarcinoma, although they are often rather hazy and ill defined (Fig. 11-8). They are located peripherally and exhibit lipidic growth, and the growth along the alveolar walls probably accounts for the relatively low density on standard radiographs. On CT, they may exhibit ground-glass opacification, particularly around the periphery of the nodule (see Fig. 11-8). The solitary nodule is associated with an excellent prognosis when it is resected at this stage. An air bronchogram may be identified on standard x-ray films and on CT. The second appearance is that of a pneumonia-like consolidation, which occurs in approximately 20% of cases (Fig. 11-9). This consolidation may be associated with nodules in the same lobe or in other lobes of either lung. This appearance reflects the presumed mode of dissemination of this tumor through the tracheobronchial tree. The third appearance is that of multiple nodules scattered throughout both lungs (Fig. 11-10). These nodules are typically 5 to 6 mm in diameter and tend to have very irregular borders. Very few patients present with this pattern of disease.
Squamous Cell Carcinoma
Clinical Features
Radiographic Features
The radiologic presentation depends on the location of the carcinoma. The most common finding is that of a central endobronchial obstructing lesion, which produces a hilar or perihilar mass (Fig. 11-11). Involvement of the central bronchus may range from focal thickening to complete occlusion. When the lesion is small, the tumor may not be evident on the standard radiograph, but the bronchial wall abnormalities are well depicted on CT (Fig. 11-12). Atelectasis or obstructive pneumonitis is usually identified distal to the obstructed bronchus. Any patient presenting with atelectasis and signs of infection should be followed radiographically to complete resolution and reexpansion of the involved lobe. Failure of resolution strongly suggests a central lung carcinoma.
Small Cell Lung Carcinoma
Clinical Features
Box 11-12 Small Cell Lung Carcinoma
ACTH, adrenocorticotropic hormone; ADH, antidiuretic hormone.
Radiographic Features
The radiographic features usually consist of a hilar or perihilar mass associated with massive, bilateral mediastinal adenopathy (Fig. 11-14). There may be associated lobar collapse. The primary tumor may not be readily evident because it is obscured by the extensive adenopathy. However, CT may show the primary tumor to better advantage. Occasionally, an SCLC manifests as a peripheral nodule that can be resected, and in these relatively uncommon cases, the prognosis is better (Fig 11-15).
Undifferentiated Large Cell Carcinoma
Staging of Lung Cancer
TNM Classification
The TNM system is widely used to classify lung tumors. In the TNM classification, T indicates the features of the primary tumor, N indicates metastasis to regional lymph nodes, and M refers to the presence or absence of distant metastasis. In 1997, the staging system was revised based on epidemiologic evidence of improved survival after surgical resection in patients who had previously been classified as having unresectable disease. However, these conclusions were derived from analysis of a relatively small database accumulated since 1975. Since then, there have many innovative changes in clinical staging with the routine use of CT and with PET imaging. The IASLC established a lung cancer staging project to analyze a much larger worldwide database of lung cancer. Following this extensive analysis, the Working Committee proposed changes to existing TNM staging system, which will be incorporated in the seventh TNM classification of malignant tumors (Tables 11-1 and 11-2).
Table 11-1 Proposed Definitions for T, N, and M Descriptors
Stage | Description |
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