Vulvar apocrine adenocarcinoma: a case with nodal metastasis and intranodal mucinous differentiation.

Primary vulvar adenocarcinomas are rare tumors, and their histogenesis is not fully understood. They are classified into extramammary Paget's disease, sweat gland carcinomas, and "breast-like" adenocarcinomas of the vulva. The latter resemble adenocarcinomas arising in the breast morphologically and immunophenotypically. Rare cases of adenocarcinoma with apocrine features have been reported, and whether these neoplasms originate from the "native apocrine" sweat glands or from "anogenital mammary-like" glands are still debatable. The presence of normal mammary-like glands in the vicinity of the tumor, the transitional malignant morphological features from normal mammary-like glands and the tumor, the breast-like histological features of the tumor, and the expression of estrogen and progesterone receptors generally suggest an origin from anogenital mammary-like glands. Absence of these features points toward native apocrine sweat glands as the source of these neoplasms. In this report, we present a patient who was initially diagnosed with Paget's disease of the right vulva, which was treated by hemi-vulvectomy, and who later presented with primary vulvar apocrine adenocarcinoma with metastasis to the inguinal lymph nodes and intranodal mucinous/colloidal differentiation: a feature, to the best of our knowledge, not reported before. We also reviewed the histogenesis of the vulvar adenocarcinomas, with emphasis on the morphological features that separate the tumors arising from the anogenital mammary-like glands in the vulva from those arising from the native vulvar sweat glands.