Abstract

Background: In 2-6% of women, ectopic breast tissue is found. Ectopic mammary tissue can go through the same degenerative processes as a eutopic breast in terms of physiological alterations. Since it only accounts for 0.3% of all breast neoplasms, ectopic breast cancer is a rare disorder that typically arises in the axilla.
Case study: We describe a unique case of a 57-year-old Tunisian woman who had a left-sided axillary lump that had been developing for almost a month. Axillary dissection was used to remove the mass-containing axillary ectopic breast tissue. A medullary multifocal carcinoma was found on pathology, and metastases were found in two lymph nodes. After six rounds of chemotherapy, she had local radiation. She had hormonotherapy and herceptin therapy. No signs of local recurrence or distant metastases have been seen after a 2-year follow-up.
Conclusion: If an axillary lump is found in ectopic breast tissue, the first diagnosis that should be explored is ectopic breast carcinoma. There are no specific recommendations for diagnosis or treatment. In order to prevent therapeutic delays, doctors should be informed of this condition. Due to the uncertain natural history of this uncommon condition, diligent patient follow-up is crucial after diagnosis.