However, most small tumors do not grow in size and lead to clinical symptoms.4 A multi-institutional study reported favorable prognosis in patients with small breast tumors despite not receiving chemotherapy.5 Despite the benign prognosis in patients with early-stage BC, the recurrence risk varied when tumors were divided into subgroups using hormone receptor and human epidermal growth factor receptor 2 (ERBB2 [formerly HER2]). This evidence concerns the gene ERBB2 and breast cancer.