Accessory breast tissue

Dr Owen Kang and Radswiki et al.

Accessory breast tissue is a relatively common congenital condition in which abnormal accessory breast tissue is seen in addition to the presence of normal breast tissue. This normal variant can present as a mass anywhere along the course of the embryologic mammary streak (axilla to the inguinal region).

Common locations

  • chest wall
  • vulva
  • axilla
  • knee
  • lateral thigh
  • buttock
  • face
  • ear
  • neck


Found in 2-6% of women and 1-3% of males 5. Although present from birth, patients are often not aware of it until puberty.

Clinical presentation

Most women are unaware of their accessory breast tissue and it is detected incidentally on a mammogram. Discomfort, pain, milk secretion, thickening of axilla and local skin irritation can occur. Accessory breast tissue responds to hormonal stimulation and may become more evident during menarche, pregnancy, or lactation. On examination, supranumerary nipples may also be seen.


This tissue ranges from a small focus of parenchyma to complete structures that include a nipple and an areola.

It is also important to remember that both benign and malignant diseases of breast tissue in ectopic locations in adult women have been described.


Accessory breast tissue can be found anywhere along the thoracoabdominal region of the milk line (embryologic mammary streak) but are most frequently found in the axilla and may occur bilaterally. Very rarely seen in the face, back and thigh.


Various disorders associated with supernumerary nipples include:

Radiographic features

Most accessory breast tissue is found coincidentally on routine screening mammography. 

Breast ultrasound

Ultrasound imaging shows breast tissue which is indistinguishable from that of the regular breast.

Breast MRI

Occasionally performed in challenging atypical cases but in practice this is rarely needed. The signal and enhancement characteristics are similar to normal glandular tissue.

Treatment and prognosis

No treatment is required in the vast majority of cases. The treatment of choice for symptomatic accessory axillary breast tissue is surgical excision as removal of the tissue will relieve physical discomfort  or mechanical discomfort in the case of large volume accessory tissue.

Accessory breast tissue should also be monitored for pathologic changes such as malignancy, fibroadenoma, mastitis and fibrocystic changes and therefore undergo the same screening as normal breast tissue. The ectopic breast tissue has been found to have a higher propensity to develop malignancy and occurs at an earlier age. Excessive breast growth (macromastia) can be seen in pregnancy as well as during adolescence.

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