The expression of this protein was observed in 194 (14.5 %) cases of BC, and it was associated with age ≥ 50 years (p = 0.043), high histologic grade (p < 0.001), high Ki-67 (p < 0.001), low levels of estrogen and progesterone receptors (both p < 0.001), and positive HER2 status (p < 0.001). This evidence concerns the gene MKI67 and breast cancer.