Flowchart with experimental design. The whole series of patients was divided into 2 major groups: a discovery group (36 patients with available frozen tissue for profiling using array technologies) and a test group (240 patients with available FFPE tissue from the diagnostic pathologic sample). The test group was further divided systematically into 2 sets of patients: the training group (123 patients) and the validation group (117 patients). The clinical characteristics according to sex, age, stage, extranodal disease, serum lactate dehydrogenase levels, electrocorticogram, and IPI score of the different sets of patients are summarized in Table 1.