Polythelia

Polythelia is the presence of one or more extra nipples along the embryonic mammary ridge, typically extending from the axilla to the groin. It may occur with or without accompanying ectopic breast tissue (polymastia). Extra nipples are usually small and may resemble a normal nipple but are often smaller and can be pigmented or hairless; most individuals are asymptomatic.

Most common location is the anterior axillary line, with occasional occurrences on the chest, abdomen, or groin. While polythelia is usually benign and cosmetic, ectopic breast tissue can rarely give rise to the same conditions as normal breast tissue, including inflammation, fibroadenomas, or carcinomas, which may be diagnosed if a mass is found and examined.

Epidemiology varies by population, with prevalence reported across a broad range. The condition arises from persistence of the mammary ridge (milk line) during embryogenesis. In some individuals, only a nipple is present; in others, there may be glandular tissue beneath the nipple along the line.

Diagnosis is clinical, based on inspection and palpation. Imaging such as ultrasound can help determine whether underlying glandular tissue is present; mammography or MRI may be used if indicated. The differential diagnosis includes benign skin lesions such as moles, nevi, or epidermal inclusion cysts.

Management is typically conservative, with treatment limited to cosmetic concerns or symptom relief. If necessary, surgical excision of the accessory nipple or involved tissue can be performed. Prognosis after removal is generally excellent; malignant transformation in accessory tissue is rare but has been reported.