MKI67 and breast cancer: These five subtypes include: luminal A (ER+, PR+, Ki67 < 20%), luminal B (ER+, PR+ or PR-, Her2+ or Her2-, Ki67 > 20%), triple-negative (ER-, PR-, HER2-), and HER2-enriched breast cancer (ER+, PR+), HER2+) (41).