Radiographic manifestations of primary bronchogenic carcinoma.

Carcinoma of the lung continues to account for more cancer-related deaths than any other neoplasm in the United States. The World Health Organization recognizes four main classifications of cell type. Squamous cell carcinoma is most often a central lesion that locally invades the hilus and mediastinum. Because of its localization within the chest, it shows the best survival statistics. Adenocarcinoma is probably the most common of the four cell types. It tends to present as a peripheral mass. Hilar, mediastinal, and extrathoracic metastases occur early in its course. Its 5-year survival rate is worse than that for squamous cell carcinoma. Alveolar cell carcinoma is considered by most to be a subtype of adenocarcinoma but demonstrates much better survival figures. Most typically it presents as a nodule, but is more often thought of as a diffuse or localized alveolar infiltrate. Large cell carcinoma resembles adenocarcinoma in that it is a peripheral mass, but often larger in size. Metastases are less frequent in large cell carcinoma than in adenocarcinoma. Large cell carcinoma demonstrates better survival figures than does adenocarcinoma. Small cell carcinoma is the most aggressive of the four cell types, having the worst prognosis. The classic presentation is the detection of hilar and mediastinal metastases while the primary tumor remains occult. Grossly enlarged hilar and mediastinal lymph nodes can be seen easily on chest radiograph and CT scan.