It is possible to have three or more breasts or nipples, a real biological phenomenon. Medically, this condition is known as supernumerary breast tissue. The presence of an additional fully formed breast is called polymastia. This is a relatively common developmental variation that occurs in both men and women. The accessory tissue can be composed of glandular tissue, a nipple, an areola, or any combination of these elements, and often goes unnoticed until hormonal changes make it more prominent.
Understanding Supernumerary Breast Tissue
Supernumerary breast tissue is categorized based on its components. Polymastia specifically describes the presence of an additional mammary gland, which may or may not include a nipple and areola complex. These accessory breasts can range from a small lump of glandular tissue to a nearly complete, miniature breast structure. A distinct but related condition is polythelia, which involves only an extra nipple or areola without underlying glandular tissue. Polythelia is much more common than polymastia, and the extra nipple often resembles a mole or a small bump. Supernumerary structures are classified into eight different types based on the presence of fat, hair, nipple, areola, and glandular tissue.
The Embryological Origin and Location
Supernumerary breast tissue formation begins very early in embryonic development, around the fourth week of gestation. At this time, a pair of thickened ectodermal lines, known as the “milk line” or “mammary ridge,” forms on the embryo. These ridges extend vertically from the armpit area down to the inner thighs. Normally, the majority of the mammary ridge regresses, leaving only the portion that develops into the two standard breasts. Polymastia or polythelia occurs when there is an incomplete regression of this embryonic tissue along the milk line. The extra tissue is typically found within the anatomical path of the original ridge. The most frequent location for supernumerary tissue is the axilla, or armpit, accounting for approximately 60% to 70% of all cases. Other common sites include the area directly below the normal breasts, the upper abdomen, and near the groin.
Functional Capacity and Health Implications
Because supernumerary breast tissue contains the same glandular elements as normal breasts, it is responsive to hormonal fluctuations. The extra tissue can swell, feel tender, or become painful during puberty, the menstrual cycle, and especially during pregnancy. Some new mothers discover accessory breast tissue only when it becomes engorged or starts to secrete milk during lactation. This ectopic tissue is susceptible to all the same conditions that affect the normal breasts. This includes benign changes like fibrocystic changes and tumors such as fibroadenomas. Although rare, this tissue can also develop breast cancer due to its similar cell structure. Malignant degeneration in supernumerary tissue is estimated to be between 0.2% and 0.6% of all breast cancers. Since the tissue is often located in unusual areas like the armpit or abdomen, a lump can be easily overlooked or mistaken for a benign fat deposit. Medical monitoring of accessory breast tissue is recommended, even if it is currently asymptomatic, due to the potential for delayed diagnosis.
Clinical Diagnosis and Treatment Options
Diagnosis often occurs during a physical examination or when a patient notices a lump or swelling. A doctor performs a detailed physical exam and takes a patient history, noting any cyclical changes related to menstruation or pregnancy. Imaging studies are used to confirm the presence of glandular tissue. An ultrasound is often the first tool employed to evaluate the structure and composition of the tissue. If malignancy is suspected, a mammogram or Magnetic Resonance Imaging (MRI) scan may be utilized for a more detailed assessment. A biopsy, which involves taking a small sample of the tissue, may be required to definitively rule out cancerous changes. Treatment depends on the tissue’s nature and the patient’s symptoms. If the tissue is asymptomatic polythelia, observation is often the only recommendation. Surgical excision is a common approach for polymastia that causes pain, significant swelling, or cosmetic distress. Removal is also advised if the tissue has been confirmed to contain a serious pathology, such as a precancerous or cancerous lesion.