This phenomenon has been observed in earlier studies, in which various molecular features were observed that were exclusively prognostic in ERG positive (SOX9, [48]; AZGP1, [49]; HOOK3, [50] or in ERG negative cancers (YB-1, [51], p16, [52], BCAR1, [53]), but not in both groups. The gene discussed is AZGP1; the disease is cancer.