mBC tumors with specific genetic mutations (e.g., human epidermal growth factor receptor 2 [HER2], PD-1, and PIK3CA) inform the use of targeted therapies or immune checkpoint inhibitors.3 Evidence suggests that, although similar in some regards, mBC differs in its biological and clinical behavior compared to female breast cancer,4 highlighting the need for more focused research to better understand its distinct characteristics and differences to improve male patients’ outcomes. The gene discussed is ERBB2; the disease is breast carcinoma.