Unusual Manifestations of Vulval Paget Disease.

Vulval extramammary Paget disease (vEMPD) is an uncommon epithelial malignancy that may arise within the vulva (primary vEMPD) or represent vulval skin involvement by a noncutaneous carcinoma (secondary vEMPD). Primary vEMPD is most often an in situ carcinoma arising within the epidermis but may be associated with dermal invasion (invasive vEMPD) or represent intraepidermal spread of an adenocarcinoma originating in vulval skin adnexa or anogenital mammary-like glands. The latter, termed mammary gland-like adenocarcinoma (MGLA), exhibits morphologic, immunohistochemical, and molecular features of various breast carcinomas but, as far as we are aware, the metaplastic variant of MGLA has not been reported on the vulva. We report 2 cases of metaplastic MGLA of the vulva with associated Paget disease and postulate that some cases of vulval MGLA may arise from Paget disease rather than originating in mammary-like glands. We also report a unique case of secondary vEMPD resulting from spread of urothelial carcinoma in situ that subsequently progressed to invasive urothelial carcinoma within the vulva.