Pilomatrix carcinoma: an immunohistochemical comparison with benign pilomatrixoma and other benign cutaneous lesions of pilar origin.

Two new cases of pilomatrix carcinoma are reported. They were studied immunohistochemically for the presence of high and low-molecular weight cytokeratins, beta-2-microglobulin, S-100 protein, carcinoembryonic antigen, epithelial membrane antigen, blood group isoantigens, and peanut agglutinin binding. Results of these studies were compared with those obtained in immunohistologic analysis of 13 typical pilomatrixomas, and 4 other benign lesions with hair follicle differentiation. An attempt was made to correlate antigenic expression with malignant transformation; however, there were no consistent differences between the 2 groups. It would seem that immunocytochemistry is of no assistance in differential diagnosis between benign and malignant hair matrical tumors. Hence, the pathologist must rely on morphological criteria alone to make a diagnosis of pilomatrix carcinoma.