MKI67 and breast cancer: A number of prognostic factors have been described with a significant relationship to likelihood of breast cancer recurrence, and commonly include patient age [1, 2], tumor size [3], lymph node status [4], and histologic grade [5], but also include biomarkers as assessed by immunohistochemistry (IHC) including Her2 status [6], patterns of hormone receptor expression (ER and PR) [7, 8], and expression of proliferative marker Ki-67 [9, 10].