Cytologic features of peripheral squamous cell carcinoma of the lung.

Cytologic features of 32 peripheral squamous cell carcinomas of the lung were reviewed. Fine needle aspiration biopsy and curettage showed most of the tumor cells to be arranged in irregular cell fragments consisting of relatively small cells with scanty cytoplasm. They possessed round to oval nuclei with coarsely granular chromatin, and some had large, prominent nucleoli. Keratinization was usually observed in small numbers of scattered cells, and a nuclear streaming arrangement was noted in some areas. When both keratinization and streaming arrangements were absent, correct subtyping was impossible (12 cases). These cytologic features were different from those of 31 hilar squamous cell carcinomas studied as controls; there many carcinoma cells showed keratinization, and small carcinoma cells were infrequent. However, in all cases, sputum cytology was correctly interpreted because squamous differentiation was easily recognized.