Accessory breast tissue

Accessory breast tissue is a normal variant and can present as a mass anywhere along the course of the embryologic mammary streak (axilla to the inguinal region).

Epidemiology

Found in 2-6% of women

Clinical presentation

Most women are unaware that they have accessory breast tissue until they get a mammogram and are told about it. Discomfort, pain, milk secretion, 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.

Pathology

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.

Location

Accessory breast tissue can be found anywhere along the milk line (embryologic mammary streak) but are most frequently found in the axilla .May be bilateral. 

Associations

Various disorders associated with supernumerary nipples, including:

• urogenital defects
• vertebral abnormalities
• hypertrophic pyloric stenosis
• testicular cancer
• aberrant ventricular conduction

Radiographic features

Most accessory breast tissue is found coincidentally on routine screening mammography. See case 18719.

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 practcie 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.

In practice

This rarely presents a diagnostic dilemma. In every day senology this is a casual observation which stays stable over time. As mentioned above all disease of the breast also occur in accessory breast tissue.