Vulva, Hidradenoma papilliferum

Hidradenoma papilliferum is the most common benign glandular tumor of the vulva. It usually presents in women between ages of 30-49 years as a single painless firm nodule less than 2 cm in diameter. Most common locations include the labia majora and interlabial folds, and less commonly in anal regions. Microscopically, they are well-circumscribed tumors consisting of complex proliferating papillae lined by a double layer of inner columnar cells and myoepithelial cells with apocrine features. They are treated with local excision and have excellent prognosis with rare malignant transformation to adenocarcinoma or adeno-squamous carcinoma.