When adjusting for one factor at a time, the largest effect on the breast cancer-specific mortality was observed when adjusting for histological grade (HR 1.09, Freedman’s % 72.0), while adjustment for HER2 (HR 1.33, Freedman’s % 7.3) and Ki67 (HR 1.35, Freedman’s % 2.4) only marginally changed the point estimate from the unadjusted analysis (Additional file 1: Table S3). This evidence concerns the gene MKI67 and breast cancer.