Hidradenoma Papilliferum With Oncocytic Metaplasia: A Histopathological and Immunohistochemical Study.

Hidradenoma papilliferum is a benign cutaneous adnexal neoplasm, commonly occurring in the vulva and perianal region of adult women. It has characteristic histopathological features composed of anastomosing and branching tubules, lined by columnar cells, and a basal layer of myoepithelial cells. A 39-year-old woman was evaluated for 2 asymptomatic labial masses. The histopathological examination revealed a Bartholin's cyst and a hidradenoma papilliferum. The latter contains a distinct area of oncocytic/oxyphilic metaplasia. Immunohistochemical stains revealed positive staining for gross cystic disease fluid protein (GCDFP)-15 and androgen receptor. GATA-3, a protein expressed in sweat glands, highlights a similar positive staining pattern with weaker staining in areas of oncocytic metaplasia. P63 highlighted the myoepithelial differentiation. In situ hybridization for Human Papilloma Virus 6, 11, 16, and 18 was negative. P53 was negative and Ki-67 was low, confirming its benign nature. Oncocytes are enlarged epithelial cells with voluminous eosinophilic granular cytoplasm resulting from staining of nonribosomal cytoplasmic components. Few reports documented it in hidradenoma papilliferum. Our case demonstrated a florid distinct appearance of this metaplasia. The immunoprofiles of this oncocytic metaplasia such as p53 negativity and positivity for androgen receptor and GCDFP-15 demonstrates similarity to apocrine metaplasia in the breast. The authors' case demonstrates the benign nature of oncocytic metaplasia and supports the common origin of oncocytic cells and columnar cells in hidradenoma papilliferum.