Pilomatrixoma is most commonly seen in the head and neck region, occurring in the first two decades of life. It varies from 0.5 cm to 3 cm in diameter. Pilomatrixoma differentiates toward hair cells. Treatment of choice is excision. A 42-year-old woman presented with a giant painful pilomatrixoma, 5 cm in diameter, in the forearm. It had gradually grown larger over a period of years. Physical examination revealed a painful, red-brown colored, ulcerative, mobile mass, 50 mm in diameter, with surrounding hyperemia. Histopathological examination of the specimen provided the diagnosis of "pilomatrixoma". The mass was totally excised, and the resultant tissue defect was repaired with a full-thickness skin graft from the inguinal area. Two years later, there was no recurrence and the postoperative scar was cosmetically acceptable. Generally, there is no recurrence if the pilomatrixoma is totally resected. The case presented in this paper is of interest because the lesion had a large diameter, appeared in the fourth decade, and had a "faceted stone" appearance with perforation of the overlying skin. It is important to differentiate this lesion from a pilomatrix carcinoma. Fig. 1 A 42-year-old woman with a painful, red-brown, ulcerative, mobile mass, 50 mm in diameter, with surrounding hyperemiaFig. 3 The 2-year postoperative result was cosmetically acceptable