Accessory Axillary Breast Tissue

Case History: 29-year-old female, five days postpartum, presented with painful swelling and palpable lump in left axillary region. Patient had no indication of fever or infection.

During the ultrasound examination, we focused on the lump and it was noted that the tissue of interest was of a different appearance than the rest of the axillary tissue. The left axillary lump was heterogeneous and the appearance of vessels or ducts inside the tissue was plainly seen. The lump measured 4.7 × 3.4 × 2.1 cm. We proceeded to put color on the area, but there was no sign of high vascularity or infection at the site. The radiologist assigned to the exam felt strongly that because of her history of just having a baby and the fact that she was lactating, that this was accessory axillary breast tissue.

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Figure 1. Left axilla – rad.

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Figure 2. Left axilla – rad with measure.

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Figure 3. Left axilla – rad with color.

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Figure 4. Left axilla – arad.

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Figure 5. Left axilla – arad with measure.

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Figure 6. Left axilla – arad with color.

Diagnosis: Accessory axillary breast tissue

Discussion: Patients with accessory axillary mammary tissue often present with complaints of pain or swelling in the involved axilla. Axillary breast tissue can also undergo monthly premenstrual changes. Symptoms may be exacerbated during pregnancy and lactation as well.

The axillary region looked exactly like breast tissue. After further discussing this exam with the radiologist, he explained that many times, this tissue has been there since birth but it will sometimes see rapid growth during pregnancy.

This normal variant can present as a mass anywhere along the course of the embryologic mammary streak (axilla to the inguinal region). Accessory breast tissue responds to hormonal stimulation and may become more evident during menarche, pregnancy or lactation. This tissue ranges from a small focus of parenchyma to complete structures that include a nipple and an areola. 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.