Atypical Ductal Hyperplasia Presenting as Vulvar Mass.

Ectopic breast tissue (EBT) is a rare condition most frequently located in the axilla and only rarely in the vulva. It can undergo similar benign or malignant changes as normal breast tissue, including rare instances of atypical ductal hyperplasia (ADH). We report a 63-year-old woman with ectopic ADH in the right labia majora, initially misdiagnosed as a benign cyst. Histopathology confirmed EBT with ADH, and subsequent re-excision showed no residual disease. Immunohistochemistry supported the mammary origin. This case highlights the importance of histological examination for vulvar lesions suspected of EBT and underscores the need for guidelines on managing these rare occurrences.