This multicenter study reported there was substantial variability in inter-laboratory reproducibility demonstrated by moderate ICC with a wide ranged 95% CI (central staining: ICC = 0.71, 95% CI = 0.47 to 0.78; local staining: ICC = 0.59, 95% CI = 0.37 to 0.68), which concluded the clinical utility of Ki67 in breast cancer to be “elusive”. This evidence concerns the gene MKI67 and breast carcinoma.