P3HR1 virus induced highly aggressive B cell lymphomas in CBH mice that stained positive for the B-cell marker CD20 and IRF4 (a marker for activated, non-germinal center B cells also known as MUM-1) (Fig 2) and invaded multiple organs including pancreas, liver, biliary tract, kidney, mesentery, abdominal lymph node, spleen and (rarely) bone (Table 1 and S1 Fig). Here, IRF4 is linked to B-cell non-Hodgkin lymphoma.