ERBB2 and breast cancer: Specimens of four molecular subtypes of breast cancer were included in the study; 49 HER2-only (ER-/ PR-/HER2+), 33 luminal A (ER+/PR+/HER2-), 39 luminal B (ER+/PR+/HER2+), and 38 triple negative (ER-/PR-/HER2-).