Fine-needle aspiration features of pilomatrixoma

BACKGROUND. Pilomatrixoma (PMX) is a benign skin neoplasm of hair matrix or igin. The fine-needle aspiration (FNA) features of PMX frequently lead to a misdiagnosis of carcinoma. METHODS. Nine cases of PMX in which a preoperative FNA was performed were r eviewed. The cytologic features were compared with the histologic appearanc e of corresponding surgical specimens as well as with cytologic features of tumors that arose in the differential diagnosis. RESULTS. Unequivocal benign diagnoses were rendered in three cases; the cor rect preoperative diagnosis of PMX was rendered in two of these cases and c onsidered in an additional case. In four additional cases, carcinoma was di agnosed or could not be excluded. A noncommittal diagnosis of epithelial tu mor, most likely of skin adnexal origin, was rendered in an additional sing le case. Retrospective review of the FNA smears in all nine instances discl osed cytologic features that corresponded well with the histologic componen ts of PMX Diagnostic cytologic features included cellular aspirates; cluste rs of small, primitive-appearing basaloid epithelial cells; a high nuclear- cytoplasmic ratio; evenly dispersed chromatin; prominent nucleoli; pink, fi brillary material enveloping clusters of basaloid cells; multinucleated gia nt cells; and sheets of ghost cells. CONCLUSIONS. The FNA cytologic diagnosis of PMX may be extremely difficult; its distinction from various primary cutaneous carcinomas is most problema tic. Recognition of a unique constellation of cytologic features in FNA sme ars in the appropriate clinical context is most helpful in making this dist inction. Cancer (C) 2001 American Cancer Society.