polymastia

Polymastia is the presence of supernumerary breast tissue beyond the usual two breasts. It results from persistence of the embryonic mammary ridge, a line of potential breast tissue that extends from the axilla to the groin. When additional glandular tissue forms, it can be accompanied by one or more accessory nipples (polythelia may occur without glandular tissue). Polymastia can occur anywhere along this milk line, most commonly in the axillary region.

Clinical features include extra breast tissue that can be unilateral or bilateral and may be complete (glandular tissue with ducts) or focal (ectopic breast tissue). It may be prepubertal, become more prominent at puberty or during pregnancy and lactation, and can be painful or tender.

Diagnosis is usually clinical. Imaging such as ultrasound or MRI may assess the extent of tissue and exclude masses. Biopsy is not typically required unless cancer is suspected. The differential includes lipomas, lymphadenopathy, and soft tissue tumors.

Management depends on symptoms and patient preference. Many cases are asymptomatic and require no treatment. Intervention is considered for discomfort, cosmetic concerns, or if there is suspicion of pathology. Treatment options include surgical excision of the accessory tissue and, if an associated nipple is present, its removal. The risk of malignant transformation in accessory breast tissue exists, but cancer is rare and managed like breast cancer in the affected tissue. Pregnancy and lactation can activate or enlarge ectopic tissue.

See also: Polythelia, supernumerary nipples, ectopic breast tissue.