Accessory breast tissue presenting as a vulvar mass in an adolescent girl

Background: The development of an accessory breast tissue is attributed to the failure of regression of milk line remnants during embryogenesis. The accessory breasts can develop anywhere along the milk line, extending from axilla to the groin. The vulvar accessory breast is extremely rare among these. Case: We report an 18-year-old girl presenting a solitary vulvar mass which is later pathologically confirmed to be an accessory breast tissue. On preoperative ultrasonographic examination, a lobulated echogenic mass with internal septa was seen in the subcutaneous fat layer of the mons pubis. Excisional biopsy was performed, which revealed an accessory breast tissue. She had no specific developmental abnormalities and had no familial history. Conclusion: An accessory breast in the vulva is an extremely rare case among the ectopic breasts, especially in an adolescent girl. Pathological confirmation is mandatory in this case to exclude a possibility of other tumor, including malignancy.