Malignant clear-cell hidradenoma associated with pseudoepitheliomatous hyperplasia on the forehead

Clear cell hidradenoma: an unusual vulvar tumor

Clear cell hidradenoma (CCH) is a benign skin appendageal tumor. Most cases occur in the skin of the head and face. The tumor usually presents as a solitary firm dermal nodule. Histologically, it is a well-circumscribed, nonencapsulated tumor formed of 2 cell types, one with clear cytoplasm and the other with dark eosinophilic cytoplasm. Although most cases are benign, occasional cases with malignant transformation have been reported. We report a case of CCH in a very unusual location. To the best of our knowledge, CCH has not been previously described in this site, in the English literature. Although rare, inclusion of CCH should be included in the differential diagnosis of benign solid and clear cell tumors of the vulvar skin.