I had always assumed that hidradenoma papilliferum (HP), which characteristically appears in the vulvar region, was derived from apocrine glands. Until I read the article by El-Khoury et al (1) I had never even heard of mammary-like anogenital glands (MLAGs).
Although it has been long known that mammary-like tissue may be present in the vulvar region, it was van der Putte (2) who popularized the concept that this tissue was not ectopic breast along the milk line, but rather distinct anogenital glands with mammary-like features. The following is the abstract from his review:
Supernumerary mammary glands derived from rudiments of the embryonic milk lines or mammary ridges in the vulva are considered a source of a series of unusual tumors resembling lesions of the breasts. This phenomenon was reevaluated in light of recent observations of mammary-like anogenital glands (MLG), which are a normal constituent of the vulva and appear to be closely related to eccrine glands. An analysis of the literature reveals that the concept of “milk lines” originated in a mixture of phylogenetic and ontogenetic theories at the beginning of this century and was not supported by observations in human embryos, which show that primordia of the mammary glands do not extend beyond the axillary-pectoral area. The breasts and the vulva are so widely separated by time and space that the vulvar MLG can not be derived from the mammary ridges or milk lines. The profile of the MLG, which can also reveal some eccrine or apocrine features, makes these glands the most likely source of a series of lesions occurring in the anogenital region and comprising lactating glands, lactating adenoma, fibroadenoma, hidrocystoma, hidradenoma papilliferum, and most cases of extramammary Paget’s disease and invasive adenocarcinoma.
El-Khoury et al analyzed 52 HPs from 47 women. The most important result is that >90% of the HPs are at the precise location of the MLAGs – the interlabial sulcus. The majority of HPs are non-ulcerated, solitary lesions, measuring < 1cm. Because of the variable presentations of HPs (pink to blue, surface ulceration, potential multilobulation), the authors are absolutely correct in stating that the diagnosis of HP may only be made histologically. Having biopsies performed is especially crucial in atypical cases, as a perusal of the literature demonstrates a variety of malignancies associated with MLAGs, such as ductal carcinoma in situ, adenocarcinoma, or tubulolobular carcinoma (PubMed July 31, 2016).
The intrigue continues. Hedayat et al report the case of a 27 year-old women with Cowden syndrome (macrocephaly, thyroid nodules, an atypical sclerosing lesion of the breast, lipoma, ganglioneuromatosis, colonic adenocarcinoma, and a PTEN mutation), who presented with a tender, polypoid perianal lesion. The biopsy demonstrated proliferative changes commonly seen in the breast, attributed to MLAGs. The authors appropriately question the concern for potential malignancy in such a patient with Cowden syndrome (3).
In conclusion, MLAGs may be responsible for significant pathology in the anogenital region. Most patients defer anogenital exams when we offer them, unless they are aware of a specific lesion at that site. Knowledge of these glands may help make our assessments more accurate.
- El-Khoury J, et al. Vulvar hidradenoma papilliferum (HP) is located on the sites of mammary-like anogenital glands (MLAGs): Analysis of the photographs of 52 tumors. J Am Acad Dermatol 2016; 75: 380-4.
- van der Putte SC. Mammary-like glands of the vulva and their disorders. Int J Gynecol Pathol 1004: 13: 150-60.
- Hedayat AA, et al. Proliferative lesion of anogenital mammary-like glands in the setting of Cowden syndrome: Case report and review of the literature. J Cutan Pathol 2016; 43: 707-10
* For those of you who know me, you might have expected me to say “The Hole Story”. Even I have my limits.