Mastopathy of the accessory breast in the bilateral axillary regions occurring concurrently with advanced breast cancer.

We herein report a 41-year-old Japanese woman who demonstrated advanced cancer in the left breast occurring concurrently with mastopathy of the accessory breast tissue in the bilateral axillary regions, which appeared to be metastatic lymphadenopathy. A preoperative examination, including a mammogram, US, and CT, did not provide us with a definite diagnosis of the axillary masses: it was essential to diagnose the masses preoperatively since a bilateral mastectomy with nodal dissection is called for if the right axillary masses are metastatic from a cancer in the right breast. An intraoperative cytological examination from the bilateral axillary masses revealed adenosis with fibrocystic changes in the accessory breast tissue. We therefore performed a modified radical mastectomy only on the left side. The patient was thus saved from an unnecessary mastectomy of the right breast. Based on our experience, we wish to emphasize that the accessory breast tissue should be considered for a differential diagnosis when evaluating the axillary masses in order to avoid over-surgery, especially when a patient has been diagnosed to have massive breast cancer. An intraoperative cytological examination is strongly recommended to reach a final diagnosis in such confusing cases.