MKI67 and breast cancer: The molecular subtyping of breast cancer can be further subdivided, according to the luminal classification, into Luminal A (ER+, PR+, HER2-, and low Ki67), Luminal B-like HER2 negative (ER+, HER2-, and high Ki67 or PR-), Luminal B-like HER2 positive (ER+, HER2+, any Ki-67, or any PR), nonluminal (HER2+, ER-, and PR-), and basal (triple negative).