In their recent publication, Modi et al. concluded that trastuzumab deruxtecan prolongs progression-free and overall survival in patients with HER2 low tumors and called for a review of current HER2 diagnostic practices, given that “more than half of patients historically categorized as having HER2-negative breast cancer” could now exhibit improved treatment outcomes [10]. The gene discussed is ERBB2; the disease is breast carcinoma.