[A Case of Ipsilateral Breast Tumor Recurrence in Which a Sentinel Lymph Node Was Identified in the Contralateral Axilla].

The patient was a female in her 80s. She had undergone Bp+SN for left breast cancer 18 years ago. This time, she was referred to our department because of suspicion of ipsilateral breast tumor recurrence. Breast ultrasound revealed a 15 mm mass in the CA area of left breast, and biopsy revealed IDC, ER+, PgR+, HER2-. The diagnosis was cT1cN0M0, Stage Ⅰ, and the treatment plan was Bt+SN. Preoperative lymphoscintigraphy revealed a single accumulation in the contralateral axillary lymph node. Surgery was performed using the dye method, and the ipsilateral axilla was searched, but no sentinel lymph node was found. However, 1 sentinel lymph node in the contralateral axilla that only had RI uptake was found. Rapid diagnosis was negative for metastasis, so axillary dissection was omitted. Contralateral axillary lymph node metastasis is classified as distant lymph node metastasis according to the breast cancer treatment guidelines. However, contralateral axillary lymph node metastasis observed at the same time as ipsilateral breast tumor recurrence may be treated as regional lymph node metastasis if it is considered to be the result of changes in lymphatic flow caused by the initial surgery.