Extramammary Paget disease is characterized by the consistent lack of estrogen and progesterone receptors but frequently expresses androgen receptor.

Extramammary Paget disease (EPD) is an uncommon cutaneous malignant neoplasm that arises in areas rich in apocrine glands (perineum, vulva, and axilla). Apocrine gland origin or apocrine differentiation of cells of EPD has been suggested. Estrongen, progesterone, and androgen hormone receptors have been reported to exhibit a characteristic pattern of expression in mammary apocrine type carcinomas; however, their expression in EPD has not been elucidated fully. By using immunohistochemical methods, we studied the expression of steroid receptors in EPD on formalin-fixed paraffin-embedded tissue samples from 28 patients with EPD without associated visceral malignant neoplasms or adnexal carcinoma. Androgen receptor (AR) was identified in 15 of 28 cases. The proportion of AR-positive cells varied from 1% to more than 75%; 8 cases expressed AR in more than 10% of cells. Strong AR expression also was seen in the invasive carcinoma arising from 1 case of EPD. All cases lacked immunohistochemically detectable estrogen and progesterone receptors. The immunophenotype characteristic of apocrine carcinomas (AR-positive, estrogen receptor-negative, progesterone receptor-negative) was seen in a substantial proportion of EPD cases. Results suggest that AR expression is a factor in pathogenesis of EPD. This may be important for the therapy of recurrent or invasive disease.