Extramammary Paget's disease (EMPD) is considered to be an intraepithelial adenocarcinoma. Typically involved anatomical sites are the vulvar, perianal, perineal, scrotal and penile regions. Clinically, the lesions present as well-defined, moist, erythematous plaques usually accompanied by pruritus. An unusual feature of EMPD is its association with cutaneous, adnexal-structure adenocarcinomas and its association with internal malignancies. Histopathological examination shows epidermal acanthosis and elongated rete ridges. Paget's cells are large intraepidermal cells with a large nucleous and abundant pale cytoplasm. Recent studies of perianal and vulvar EMPD have described distinct immunohistochemical subtypes termed cutaneous and endodermal. Cutaneous EMPD is characteristically positive for cytokeratin (CK)7, negative for CK20, and positive for gross cystic disease fluid protein (GCDFP)15+, whereas endodermal EMPD shows a CK7+ CK20+ GCDFP15- phenotype. Surgery remains the treatment of choice, with either wide surgical excision or Mohs' micrographic surgery. We present a case of EMPD with an underlying carcinoma, which combined immunohistochemical findings suggestive of the cutaneous subtype (positive for CK7, GCDFP15, mucin (MUC)1, human epidermal growth factor receptor (HER)2/neu positive) and the endodermal subtype, frequently associated with internal malignancy (CK20, MUC2, CDX-2 positve); however, our patient had no associated internal malignancy.

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