MKI67 and breast carcinoma: The DDFS durations of the 854 women with low Ki-67 expression and low PgR levels (that is, those who were reclassified as having luminal B–like instead of luminal A–like breast cancer according to the 2013 definitions) were similar to those of the 2,315 women with low Ki-67 expression and high PgR levels (that is, those who remained classified as having luminal A–like breast cancer) (hazard ratio (HR) = 1.05, 95% confidence interval (CI) = 0.67 to 1.65; P = 0.80 by Gray test) (Figure 2a).