Fibroadenoma of the vulva with pseudoangiomatous stromal hyperplasia: A common neoplasm in uncommon site.

Mammary-type tissue in the vulva was first described in 1872 but has been rarely reported in the literature. This tissue was previously considered as ectopic breast tissue that occurs as a result of incomplete regression of the milk line. Similar to native breast tissue, ectopic mammary tissue is hormone-sensitive and can develop benign changes, such as fibroadenoma, as well as malignant changes. A more recent theory suggests that these benign and malignant mammary-type entities arise from mammary-like anogenital glands, which constitute normal vulvar components. We report a case of a 41-year-old woman who presented with a chronic asymptomatic cyst on the left vulva that eventually became uncomfortable, especially on standing. The cyst was located on the labium minus, measuring 1.0 × 0.5 cm, with no identified erythema or other skin abnormalities. Excision of the lesion and subsequent microscopic examination showed a circumscribed mass with a nodular overgrowth of epithelial and stromal components, resembling a mammary fibroadenoma with pseudoangiomatous stromal hyperplasia. We bring to attention this rare diagnosis and the importance of considering it in the presence of a vulvar lesion. The malignant and recurrence potential of mammary-type tissue necessitates excision with clear margins and close monitoring of these patients.