Primary adenocarcinomas of the vulva and related structures: An enigmatic and diverse group of tumors✰

Approximately half of adenocarcinomas that involve the vulva are secondary, either through direct extension or metastases from elsewhere. Primary vulvar adenocarcinomas are rare and encompass a diverse array of neoplasms that are nominally classified based on the presumed tissue or organ of origin, the tumoral phenotype, or both. In this review, we summarize the clinicopathologic features of adenocarcinomas that originate from the vulva and related structures, including the terminal urethra. Adenocarcinomas of this region encompass lesions that are defined by their primary site (such as adenocarcinomas of the Bartholin gland, which by definition must be in the region of the Bartholin gland), histomorphology and immunophenotype (such as clear cell carcinoma and adenocarcinoma of intestinal [cloacogenic] type), or both (such as adenocarcinoma of skene gland origin, which is associated with that specific organ but which also displays a distinctive phenotype that is similar to the phenotype of high grade prostatic adenocarcinoma). Other types, such as mammary-type adenocarcinomas, are presumed to originate from the putative mammary-like glands of the vulva and display a spectrum of pathologic features that are similar to their mammary counterparts. Similarly, vulvar carcinomas of sweat gland origin are pathologically similar to their counterparts in the non-vulvar skin and include a variety of cutaneous adnexal-type malignancies such as apocrine adenocarcinoma and eccrine adenocarcinoma. Some tumors, such as adenoid cystic carcinoma, may represent a Bartholin gland adenocarcinoma, a carcinoma of sweat gland origin, or a carcinoma arising from extramammary Paget disease (EMPD), depending on the context. Invasive carcinomas of various types have been reported in 7–12.7% of EMPD, and these are likely the most common primary glandular malignancy of the vulva. Occasional vulvar adenocarcinomas have been reported to be HPV-associated, although this association has not been established for the broader group of vulvar adenocarcinomas. Rare adenocarcinomas are not classifiable by the aforementioned nosologic scheme, and are designated as vulvar adenocarcinoma NOS.