Mature B‐cell lymphoma TMAs including MZL (n = 59, see Table I), FL (n = 51), MCL (n = 31), DLBCL (n = 139), and PCNSL (n = 33) were immunostained for the presence of HRG in the tumor compartment (Figure S1). The gene discussed is HRG; the disease is primary central nervous system lymphoma.