Difficult-to-Diagnose Hormone-Negative, Human Epidermal Growth Factor Receptor 2-Positive Poorly-Differentiated Breast Cancer in a Male Patient

Male breast cancer is rare, accounting for approximately 0.5-1.0% of all cases and is often a hormone-dependent luminal type. The percentage of hormone-negative, human epidermal growth factor receptor 2 (HER2)-positive breast cancer cases is very small in male patients (0.6-1.2%), and the prognosis is generally poor.