[HER2-Positive T1a Breast Cancer Metastatic to the Liver and Brain in a Patient Who Died Four Years and Three Months after Mastectomy--A Case Report].

The prognosis of patients with T1a breast cancer is generally good, with a 5-year overall survival rate of 95%. However, HER2 overexpression is a risk factor for recurrence. A 46-year-old woman with left breast cancer underwent a total breast resection. The resected specimen showed invasive ductal carcinoma (T1a, NX, MX, g, ly0, v0, ER [-], PgR [-], HER2 [3+], Ki-67 20%). The patient did not receive adjuvant chemotherapy based on treatment guidelines. Nine months after the mastectomy, multiple liver metastases and severe acute hepatic insufficiency were found. The patient received chemotherapy with trastuzumab and paclitaxel, and a complete response was observed with disappearance of the liver metastases. One year and 11 months after the mastectomy, multiple brain metastases appeared. The patient received whole brain radiation therapy, Gamma Knife radiosurgery, and Cyber Knife radiosurgery. However, the brain metastasis could not be controlled, and the patient died 4 years and 3 months after mastectomy. HER2 positive T1a breast cancer should be observed carefully, and treatment with trastuzumab should be considered.