Primary cutaneous apocrine carcinoma arising within a nevus sebaceus.

Nevus sebaceus (NS)(organoid nevus) is a benign follicular neoplasm that commonly occurs on the scalp, face, or neck. With time, it may give rise to benign or malignant tumors such as trichoblastoma, syringocystadenoma papilliferum, and basal cell carcinoma (BCC). Rarely, other types of neoplasms may develop. We present a 76-year-old woman with several trichoblastomas as well as a primary cutaneous apocrine carcinoma arising within a preexisting NS that was treated with frozen section excision.