ERBB2 and breast carcinoma: As documented by previous research, breast cancer with low HER2 expression can be defined as a new subtype of breast cancer, which has its own biological characteristics and is different from other types in treatment response and prognosis.6 The present study was performed to have a better understanding of the clinical characteristics of breast cancer patients with low HER2 expression, so as to provide a better prognosis and treatment basis for breast cancer with low HER2 expression.