Trichoblastoma and sebaceoma in nevus sebaceus.

We report two cases of an unusual combined adnexal neoplasm arising in a nevus sebaceus (NS). Clinically, both neoplasms presented in two women (46 and 78 years) as single, partially ulcerated nodules within NS situated on the scalp. Histopathologically, each neoplasm showed distinctive aggregations of basaloid cells with features of trichoblastoma adjacent to aggregations of neoplastic cells exhibiting features of sebaceoma. In both cases, typical features of NS were present. To the best of our knowledge, this unusual combined adnexal neoplasm comprised of trichoblastoma and sebaceoma could not be assigned to any previously described histopathologic entity. This "complex" adnexal neoplasm should be distinguished histopathologically from basal cell carcinoma with sebaceous differentiation and trichoblastoma with sebaceous differentiation.