A case of ectopic breast cancer with a literature review

A 63-year-old woman was referred to our hospital because of a right axillary nodule in 2004. Physical examination showed a spherical nodule measuring 0.5 cm in diameter in the right axilla. No mass was palpable in either breast. Mammograms were normal. Ultrasonography revealed a subcutaneous hypoechoic mass 0.7 mm in maximum diameter in the right axilla. The patient underwent an excisional biopsy. Histological examination revealed an invasive ductal carcinoma (scirrhous carcinoma) in ectopic breast tissue. The patient subsequently underwent a wide local excision of the tissue surrounding the biopsy scar, with axillary lymph node dissection. Histologically, no residual tumor or nodal metastasis was found. Postoperatively, she received endocrine therapy and remains well, without any evidence of recurrence 4 years 10 months after operation. Cancer of the ectopic breast tissue is rare, and most cases present as a solitary axillary mass. Long-term outcomes remain unclear. We present a case of breast carcinoma in the axillary ectopic mammary gland and summarize the clinical features of 94 cases, including ours, in Japan. We also compare long-term survival between ectopic breast cancer and usual breast cancer according to TNM T stage and lymph node metastasis.