Papillary hidradenoma

Papillary hidradenoma
Other names	Hidradenoma papilliferum
Micrograph of a papillary hidradenoma with papillary structures; fragmented overlying epidermis is at the top of the image. H&E stain.
Specialty	Gynecology, dermatology
Symptoms	Mass in the genital or other area
Treatment	Surgical removal
Prognosis	Excellent

A papillary hidradenoma, also termed hidradenoma papilliferum or mammary-like gland adenoma of the vulva,^[1] is a rare, but nonetheless most common benign tumor that occurs in and between anal and genital regions (i.e. anogenital area) of females.^[2] These hidradenomas are sharply circumscribed, nodular tumors that usually develop in women's anogenital area (particularly the vulva^[3]) but uncommonly occur in other sites in women and men.^[4] Papillary hidradenomas that develop outside of the anogenital region are termed ecctopic papillary hidradenomas or ectopic hidradenoma papilliferums.^[5]

Anogenital papillary hidradenomas are regarded as tumors that form in anogenital mammary–like glands (MLAGs); MLAGs are a type of apocrine gland.^[2][6] MLAGs were once classified as abnormally located breast tissue glands (see accessory breast tissue@ https://doi.org/10.53347/rID-11125) but are now considered to be normal components of the anogenital region. Microscopically, papillary hidradenomas often resemble certain types of breast tumors.^[2] Ectopic papillary hidradenomas are thought to be tumors of apocrine glands which have an as yet unclear relationship to MLAGs.^[7]

Typically, papillary hidradenomas are solitary, slow-growing, small tumors that may have been present for months to many years before the time of diagnosis.^[8] The tumors are usually symptomless but may be intermittently or constantly painful, become ulcerated, and exhibit minor levels of bleeding.^[9] The pain resulting from these tumors may be simple tenderness, more or less constant usually mild pain,^[4][9] or, in females, dyspareunia, i.e. pain during and just after sexual intercourse.^[4]

Rarely, papillary hidradenomas have progressed to what appear to be 1) in situ malignancies (i.e. malignancies that have neither metastasized nor invaded beyond the layer of tissue where they arose); 2) locally invasive malignancies;^[10][11] or 3) complex tumors intermixed with other malignancies such as extramammary Paget disease, melanoma, and squamous cell carcinoma.^[8] Furthermore, benign papillary hidradenoma tumors may be confused clinically with cancerous tumors^[12] and recent studies have indicated that other types of tumors have often been mistakenly diagnosed as papillary hidradenomas.^[13] Papillary hidradenomas, particularly ectopic papillary hidradenomas, require further study to better define the criteria for their diagnosis.^[13]