In our study, the expression of IDO1 and IDO2 differed between DLBCL and NK/TCL, indicating that IDO1/2‐targeted therapy might have a better effect in NK/TCL than in DLBCL and that TDO2 may play a more vital role in DLBCL than in NK/TCL. The gene discussed is IDO1; the disease is diffuse large B-cell lymphoma.