Hidradenoma papilliferum of the vulva in association with an anogenital mammary-like gland.

Hidradenoma papilliferum (HP) is a benign adnexal neoplasm which preferentially develops in the anogenital region of women. Although the origin of HP was previously thought to be an apocrine sweat gland, recent studies have suggested that it may derive from the anogenital mammary-like gland (MLG). In this paper, we present a 43-year-old Japanese woman with hidradenoma papilliferum of the vulva. The lesion developed 7 years prior to her visit, and clinically appeared as a skin-colored cystic nodule. Histopathological examination revealed that the neoplasm was formed by the tubular structures consisting of two types of pleomorphic cells, columnar cells in the luminal layer and cuboidal cells in the basal layer. Further, the surgical specimen contained a wide, divergent, lobular ductal structure located in the vicinity of the neoplastic lesion, which was consistent with MLG.