Clinicopathologic characteristics of peripheral squamous cell carcinoma of the lung.

Squamous cell carcinoma of the lung can be divided into two types according to the location of the primary site: the central type and the peripheral type. The clinicopathologic factors in the peripheral type of lung squamous cell carcinoma have not yet been fully evaluated. A total of 204 surgically resected lung squamous cell carcinomas were reviewed with special reference to their location, histologic characteristics based on tumor growth patterns, and clinicopathologic factors. The central type and the peripheral type accounted for 95 and 109 cases, respectively. Although the patient population of the peripheral type was older, with a lower pathologic stage, lower lymphatic vessel involvement, and lymph node metastasis, the Kaplan-Meier survival proportions did not differ significantly between these two groups. Based on the histologic growth pattern, the peripheral type was classified under three subgroups as follows: 1). the alveolar space-filling type, 2). the expanding type, and 3). the combined type. Among these three types, the alveolar space-filling type showed neither lymphatic vessel invasion nor lymph node metastasis and had the most favorable prognosis. The central and peripheral types of lung squamous cell carcinoma have different clinicopathologic characteristics and should be classified under respectively different categories.