Non-anogenital (ectopic) hidradenoma papilliferum with sebaceous differentiation: a case report and review of reported cases.

Hidradenoma papilliferum is a benign tumor that usually occurs in the female anogenital region. We present a 52-year-old male with a non-anogenital (ectopic) hidradenoma papilliferum on his face. He had had a subcutaneous tumor on his right eyebrow for 30 years. The histological findings included variously shaped cystic and tubular structures in the tumor. The lumina were surrounded by a double layer of cells and showed active decapitation secretion. The lesion contained sebaceous differentiation, which has not been previously documented in the histopathology of hidradenoma papilliferum. We review the published work of non-anogenital (ectopic) hidradenoma papilliferum tumors on the head and neck.