Trichoblastoma and sebaceoma in nevus sebaceus

We report two cases of an unusual combined adnexal neoplasm arising in a ne vus sebaceus (NS). Clinically, both neoplasms presented in two women (46 an d 78 years) as single, partially ulcerated nodules within NS situated on th e 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, typic al features of NS were present. To the best of our knowledge, this unusual combined adnexal neoplasm comprised of trichoblastoma and sebaceoma could n ot be assigned to any previously described histopathologic entity. This "co mplex" adnexal neoplasm should be distinguished histopathologically from ba sal cell carcinoma with sebaceous differentiation and trichoblastoma with s ebaceous differentiation.