The student will be able to define and describe bronchogenic carcinoma, distinguishing its various subtypes.
The student will be able to define and describe bronchial carcinoid tumor, distinguishing typical from atypical subtypes.
The student will be able to identify the most common benign lung tumor, the most common malignant lung tumor, and the most common primary neoplasm in cancer-related death in the United States.
Although some use the term "tumor" as a synonym of neoplasm, its core meaning is swelling or mass. Using this broader definition of "tumor," lung tumors include non-neoplastic masses, as well as benign and malignant neoplasms.
The most common benign lung tumor is a pulmonary hamartoma, typically a popcorn-shaped mass of cartilage, fat, fibrous tissue, and blood vessels (Fig. 31.1). A hamartoma is a non-neoplastic mass of tissue in a normal anatomic location but with abnormal architecture. Despite its name, cytogenetic evidence suggests that the pulmonary hamartoma is neoplastic. Benign neoplasms of the lung include fibroma (a proliferation of spindle cells resembling mature fibroblasts), leiomyoma (a proliferation of spindle cells resembling mature smooth muscle cells), hemangioma (a proliferation of mature endothelial cells forming blood vessels of variable size), chondroma (a proliferation of cells resembling mature chondrocytes admixed with chondroid extracellular matrix), and inflammatory pseudo-tumor (a myofibroblastic proliferation).
Pulmonary hamartoma. (a) Grossly, pulmonary hamartoma consists of a well-circumscribed lobulated mass with a shiny cut surface. (b) Histologically, the hamartoma shows islands of cartilage (large arrows) associated with bronchial epithelium (small arrows). From Rosai and Ackerman's Surgical Pathology, 9th ed., Mosby-Elsevier, 2004.
The most common malignant neoplasm in the lung is a metastasis. Among primary malignant neoplasms of the lung, 90%-95% of these are derived from bronchial epithelium and are collectively referred to as bronchogenic carcinoma; the remaining 5%-10% of primary malignant pulmonary neoplasms comprise a heterogeneous group of cancers. Unless otherwise specified, the term "lung cancer" typically refers to bronchogenic carcinoma rather than metastasis or non-bronchogenic malignancies.
Excluding non-melanoma skin cancers (squamous cell carcinoma of the skin and basal cell carcinoma of the skin), bronchogenic carcinoma represents the second most common cancer in the United States (see Fig. 32.1) and the most common cause of cancer-related death in men and women. The development of bronchogenic carcinoma is a multistep process in which numerous specific mutations accumulate in a temporal sequence. Common oncogenes involved in the pathogenesis of bronchogenic carcinomata include c-MYC, k-RAS, EGFR, c-MET, and c-KIT. Tumor suppressor genes that are commonly deleted or inactivated in the pathogenesis of bronchogenic carcinoma include p53, RB, p16, and unknown genes on the short arm of chromosome 3. Risk factors for the development of bronchogenic carcinoma are discussed in Chap. 32 and ...