Expression of MUM1 and PRDM1/Blimp1 demonstrates an inverse association with MHC II. Protein expression scores (a.u. indicates arbitrary units) using chromogenic IHC were calculated as described in “Chromogenic IHC” (possible range, 0-7) and compared between cases of DLBCL with MHC II < 50% or > 50% as defined by GEP. (A) Cases with MUMI protein expression of 5 a.u., were all in the bottom 50% of MHCII expression. (B) Cases with PRDM1/Blimp1 protein expression of 2-3 were all in the bottom 50% of MHCII expression.