Invasive breast cancer in ectopic axillary breast tissue — case report

Breast cancer is the most commonly diagnosed malignancy in women in Poland. Rare, unusual forms of breast cancer remain a diagnostic problem. The incidence of ectopic breast glandular tissue in the general population varies between 0.4 and 6%. The same abnormalities and diseases as in the anatomical mammary gland may develop in this tissue. Breast cancer may develop as well. We present the case of a 36-year-old woman, who went to the doctor because of a nodule in the right armpit presented for 2 years. The patient was referred to a surgeon with suspicion of an epidermal cyst. The lesion was surgically removed and in the histopathological examination, the diagnose was: invasive breast cancer in ectopic glandular tissue. After imaging diagnostics, discussion of a multidisciplinary diagnostic and therapeutic team, the patient was offered a surgical procedure - widening of the excision margins to obtain oncological completeness and axillary lymphadenectomy. After the surgery, due to the results of the histopathological examination, complementary systemic treatment (chemo- and hormone therapy) and radiotherapy were used. Doctors often do not consider the possibility of primary breast cancer occurring elsewhere than in the breast. Breast imaging does not always make it possible to diagnose the disease, and doctors performing and interpreting these tests often do not include primary armpit cancer in the differential diagnosis. This can cause a delay in diagnosis and worsen the prognosis.