The HR+/HER2+ (Luminal B), triple-negative, and HR-/HER2+ subtypes, found in higher proportions among AYAs [6], generally are associated with worse survival than the HR+/HER2- (Luminal A) subtype [15,16], which could explain the overall poor prognosis reported for AYA breast cancer patients. The gene discussed is ERBB2; the disease is breast cancer.