Follicular Lymphoma : Grade 3b
Grade 3 follicular lymphomas (FLs) have greater than 15 centroblasts/hpf. In Grade 3a subtype, centrocytes are still present. In Grade 3b subtype, there are solid sheets of centroblasts as shown in this image. Centrocytes are not present. Grade 3b cases often show diffuse areas devoid of follicles which should be diagnosed as diffuse large B-cell lymphoma (DLBCL). When areas of DLBCL are found in lymph nodes showing FL, the primary diagnosis in such cases should be DLBCL with a secondary diagnosis of FL. The relative proportion of each tumor type should be mentioned.