Metastasizing adenocarcinoma and multiple neoplastic proliferations arising in a nevus sebaceus.

Nevus sebaceus of Jadassohn is a hamartoma of multiple skin structures. Many neoplasms have been reported to arise in association with nevus sebaceus, most commonly trichoblastoma/basal cell carcinoma and syringocystadenoma papilliferum. We report a case of a 66-year-old woman with an adenocarcinoma as well as multiple neoplastic proliferations arising in a long standing nevus sebaceus on the scalp, with subsequent occipital neck metastatic disease. On histologic evaluation, the epidermis showed changes reminiscent of tumor of the follicular infundibulum as well as basaloid proliferations resembling superficial trichoblastoma. A focus suggestive of syringofibroadenoma was also present. A small dermal collection of basaloid and more mature sebocytes was consistent with a sebaceoma/sebaceous epithelioma. Most of the lesion was composed of an adenocarcinoma with areas showing ductal differentiation with decapitation secretion, well-formed papillae and focal cribriform structures. Other portions demonstrated a high-grade neoplasm with prominent nuclear atypia and a solid pattern of growth resembling high-grade breast carcinoma. Anti-epithelial membrane antigen strongly labeled tumor cells and highlighted ductal structures. Less than 1% of cells expressed progesterone or estrogen receptors. Her2/neu reactivity was focally present, showing 1+ membranous reactivity in 10% of cells. Anti-p63 labeled basaloid cells surrounding the tumor lobules. A breast primary was ruled out by clinical and radiologic examination. This report illustrates an extraordinary case of adnexal neoplasia displaying various lines of differentiation arising in association with nevus sebaceus.