Primary breast cancer of the vulva.

Adenocarcinoma originating in a focus of mammary tissue in the vulva is an extremely rare occurrence. Only three such cases have been reported in the literature. Herein, the fourth example of a primary cancer developing in vulvar mammary tissue is described. Extension to regional lymph nodes is documented, as well as the presence of estrogen receptors in this tumor. Immunohistochemical evidence is rendered supporting an origin from mammary anlage.