Abstract

We report and immunohistochemically document the first (to the best of our knowledge) case of malignancy in which an intraductal carcinoma resembling apocrine breast cancer arose within a papillary hidradenoma of the vulva. Papillary hidradenoma is generally thought to originate from apocrine sweat glands, but a derivation from milk line remnants of the vulva should also be considered. Immunoreactivities for low- and high-molecular-weight cytokeratins, alpha-smooth-muscle-specific actin, carcinoembryonic antigen, S100 protein, and gross cytic disease fluid protein 15, an antigen of apocrine differentiation, show features that resemble those of an intraductal apocrine breast cancer. Positivity for gross cystic disease fluid protein 15 as well as the presence of estrogen and progesterone receptors suggest that tumor cells are controlled by ovarian steroid hormones. To our knowledge, no cases of malignancy arising from a papillary hidradenoma have been proved to date. Therefore, we also discuss previously reported cases of putative cancers that have developed in papillary hidradenomas. In the case presented herein, a local excision with a narrow rim of surrounding tissue was performed, and the patient was alive and well, without signs of recurrence, after 2 years of follow-up.