Hidradenoma papilliferum: Everyone else's diagnosis

A 52-year-old female presented with an asymptomatic cyst-like lesion on her right labia majora present for several years. Excision revealed a 3-mm cystic lesion containing complex networks of thin fronds of clear apocrine cells and basaloid cells, features characteristic of hidradenoma papilliferum (HP). In contrast to the medical literature, the lesion was connected to the overlying epithelium by a straight duct, a feature characteristic of apocrine glands. Searching of six different dermatopathology study sets revealed 11 cases diagnosed as HP. Histological review of the eight available cases for review revealed none that were diagnosed correctly. Six were syringocystadenoma papilliferum and two were trichoepithelioma. HP is a fascinating lesion that needs further study and requires better diagnostic criteria.