Ultrastructure of spindle cell squamous carcinoma.

A 63-year-old white male presented with a nine-month history of a nontender ulcerated lesion on his ear. Light microscopy demonstrated a moderately well circumscribed lesion in the dermis which abutted upon epidermis. There was no evidence of continuity between the tumor and overlying epithelium. The tumor was very cellular with an admixture of cells - spindle, polyhedral and bizarre giant cells. Mitotoc figures were abundant and frequently abnormal. We interpreted this lesion to have the clinical and pathologic features of an atypical fibroxanthoma (AFX). Ultrastructure, however, showed abundant tonofilaments and desmosomes indicative of an epithelial origin and therefore most consistent with a spindle cell squamous carcinoma (SCSC). It is urged that, when possible, electron microscopy be performed on problematic cases diagnosed either as an AFX or spindle cell squamous carcinoma since it is the most valid basis on which a correct diagnosis can be made.