From 1986 to 1991, 46 specimens of proliferating tricholemmal cystic carcinoma were received in the dermatopathology laboratory at New York University. Eighty percent of the patients who bore the neoplasm were over 40 years of age, the range being 26 to 81 years. Women were affected twice as often as men, and the majority of the lesions presented themselves as a solitary mass. No more than two nodules were found in any single patient and the presence of more than a single lesion was distinctly uncommon. The scalp was the most common site, followed in descending order of frequency by the face and trunk. The commonest clinical diagnosis submitted along with these specimens was "sebaceous cyst" or "pilar cyst." In other large series, information about the patients themselves and the neoplasms themselves is comparable to that in our own.^{12,16–18,21–23} Proliferating tricholemmal cystic carcinoma also has been observed on the scapula,²⁴ thorax,²⁵ leg,²⁶ forearm,²⁷ and in the lumbar area.²⁸ It may become exceedingly large, attaining a size of up to 25 cm in diameter,^11,29 and be multinodular; it may become eroded or ulcerated; and it may develop in a nevus sebaceus.^30,31