diffuse large b cell lymphomadiffuse b cell lymphoma prognosisstage 4 diffuse large b cell lymphomadiffuse large b cell lymphoma dlbcldiffuse large b celldiffuse b cell lymphoma survival rateb cell lymphoma diagnosislarge b cell lymphoma prognosisb cell lymphocytic lymphomab cell malignant lymphomaaggressive large b cell lymphomafollicular b cell lymphoma