We report a case performed mastectomy to tumor progression of breast cancer omitting surgery after neoadjuvant chemotherapy. A 62-year-old female patient visited our hospital for left breast tumor. A tumor of the size of 26×24 mm was found at between lower and upper outer quadrant, and we diagnosed it as breast cancer(cT1, cN2, M0, Stage ⅢA, ER positive/HER2 positive). Neoadjuvant chemotherapy by triweekly trastuzumab and weekly paclitaxel followed by EC chemotherapy were performed. However, she rejected surgery after neoadjuvant chemotherapy, and although we consequently restarted a regimen of triweekly trastuzumab which she also refused to continue after 9 cycles. 32 months later, she noticed induration on her left breast, and we diagnosed it as tumor progression of breast cancer. After obtaining informed consent, we performed total mastectomy and axillary lymph node dissection. Histological diagnosis revealed invasive ductal carcinoma, ER negative/HER2 positive, and no axillary lymph node metastasis. So far omission of surgery after neoadjuvant chemotherapy to breast cancer is not defined yet, and we expect early definition of evidence.