We also found statistically significant differences in the distribution of women with early and late menarche between BC and control groups (P = 0.023, OR = 3.59, 95% CI [1.26–10.18]), and an inverse correlation between the level of Ki-67 and the age of BC patients (Spearman’s rho = −0.507, P = 0.0019). This evidence concerns the gene MKI67 and breast cancer.