Another study, which compared 319 patients from the German ACC Registry with 250 patients in a validation cohort found Ki-67 to be the single best prognostic value for RFS (HR for recurrence, 1.042 per 1% increase; p < 0.0001) and OS (HR for death, 1.051; p < 0.0001) [36]. This evidence concerns the gene MKI67 and adrenal cortex carcinoma.