Consort diagram outlining patients with DLBCL with tissues tested for gene expression. The discovery cohort consisted of 163 patients with histologically confirmed DLBCL from the Princess Alexandra (PA) Hospital (n = 68), and the Canberra Hospital (n = 95) identified from a prospectively maintained clinical lymphoma database. All patients received chemoimmunotherapy with R-CHOP and otherwise were selected solely by availability of formalin-fixed paraffin-embedded tissue for RNA extraction and clinical annotation (including survival data). Findings were validated in an independent cohort of 146 patients treated with R-CHOP. This contained cases identified at the Royal North Shore (RNS) Hospital, Sydney (n = 84) from a prospectively maintained clinical lymphoma database and 62 patients from the Australasian Leukaemia and Lymphoma Group (ALLG) Biobank for whom outcome data were available. For the expansion cohort (used for association and correlation analysis), discovery and validation tissues (n = 309) were combined with 68 de novo DLBCL samples from the ALLG Biobank for which baseline clinical information and tissue data, but not outcome data, were available (total 377 tissues).