Primary glandular malignant tumors of the vulva represent about 1% of the total vulvar cancers, and those originating from the vulvar mammary-like tissue are even rarer. These are locally aggressive tumors that frequently recur. Metastatic tumors comprise approximately 8% of all vulvar tumors and should always be ruled out first before rendering the diagnosis of a primary glandular malignant tumor of the vulva.

Case details.

A 55-year-old female with a 3.2-cm hard reddish lesion on right labia majora underwent an excisional biopsy and showed a tumor with morphology favoring high-grade adenocarcinoma. IHC panel showed ER, CK7, and GATA3 as well as synaptophysin positivity.

A diagnosis of adenocarcinoma of mammary gland type (AMGT) located in the vulva requires histopathologic evidence of mammary-like tissue, through morphology and immunohistochemical markers (such as hormone receptors, GATA3, and appropriate cytokeratin profiles) along with clinical and radiological exclusion of primary breast carcinoma.

When confronted with a vulvar mass, if the tumor resembles breast carcinoma morphologically, the possibility of adenocarcinoma of mammary gland type (AMGT) should be considered. Neuroendocrine differentiation is common in non-neuroendocrine carcinomas and a tumor should not be labeled as large cell neuroendocrine carcinoma if the morphological features are absent.