MKI67 and breast cancer: The resulting molecular subtypes are HER2-enriched (ER-, PR-, HER2+), triple-negative (TN) BC (ER−, PR−, HER2−), and two luminal types: Luminal A (low Ki-67, ER+ or PR+, HER2−) and Luminal B (high Ki-67, HER2+) (Zhang et al., 2023).