In addition, the study showed that the 5-year recurrence and metastasis risk of HER2+ and T1abN0M0 patients was 5 times greater than that of HER2-low patients, suggesting that small-tumor, lymph node-negative, HER2+ BC patients still had a greater recurrence risk than small-tumor, HER2-low BC patients. The gene discussed is ERBB2; the disease is breast cancer.