Hidradenoma papilliferum with mixed histopathologic features of syringocystadenoma papilliferum and anogenital mammary-like glands.

A case of hidradenoma papilliferum with mixed features of syringocystadenoma papilliferum (SCAP) and anogenital mammary-like glands is reported. A single, fresh red-colored nodule developed in the sulcus between the labia majora and minora of a 49-year-old Japanese woman. Histopathologically, the tumor showed epithelial lining with apocrine secretion and slight connective tissues characteristics. Our case was unique because, like SCAP, the tumor was connected to the epidermis and cystic invaginations extended downward into the deep dermis. In addition, beneath the tumor, tubular structures that resembled normal mammary tissue were present in the subcutaneous fatty tissue. In this study, it has been suggested that this tumor might have been developed from these mammary-like glands.