Abstract
A 48-year-old woman noticed a red-brown nodule (2cm in diameter) on her right chest wall about six months before seeking medical attention. Histopathologically, the nodule consisted of adenoid proliferation of atypical cells. Metastatic cancer was considered, but examinations did not detect other primary tumors, and the nodule was surgically removed with a 1cm wide margin. Because fragments of normal appearing mammary gland were detected under the tumor nest in the resected specimen, a diagnosis of breast cancer arising from an accessory mammary gland was made. Immunohistochemical examination demonstrated that the tumor cells were positive for estrogen receptor, progesterone receptor, and HER 2 (human EGFR related protein 2). Sentinel lymph node biopsy performed during subsequent extended surgery demonstrated metastasis in a lymph node, and total lymph node resection was performed. The patient underwent radiotherapy and chemotherapy, and no local recurrence has been observed to date. When nodules or tumors are observed on the skin along the milk line, the possibility of cancer arising from accessory mammary gland should be considered
