Skin adnexal tumor pilomatrix disease: a transformation from benign to malignant.

Skin adnexal tumors are a wide category of both benign and malignant neoplasms that exhibit morphologic differentiation into one or more than one type of adnexal structure of the skin. We present here a unique finding of a large pilomatrix carcinoma (PC) of the upper extremity in a 54 year-old-man, initially believed to be a pilomatricoma (PM). He underwent surgical excision and lymph node biopsy successfully without any complications followed by reconstructive skin grafting. Imaging and initial pathology supported a benign diagnosis, however further tissue analysis revealed a malignant PC with evidence of matrical differentiation, increased mitotic activity, and central necrosis. Our patient's disease course may support the theory that benign PM are the origin of formation of PCs. Furthermore, this case report will discuss the histology, epidemiology, and evolving pathogenesis of these adnexal tumors.