*6.8.1 Morphology and immunophenotype*

DLBCL usually shows a diffuse pattern of growth by a monotonous population of large cells that have a round or oval nucleus that appears vesicular due to margination of chromatin to the nuclear membrane, but large multilobated or cleaved nuclei are prominent in some cases. The cytoplasm is usually moderately abundant and may be pale or basophilic (**Figure 8**). More anaplastic tumors may even contain multinucleated cells with large inclusion-like nucleoli.

DLBCL express CD19 and CD20 and show variable expression of germinal center B-cell markers such as CD10 and BCL6 and for markers IRF4 (interferon regulatory factor4) and MUM1 (melanoma associated antigen (mutated) 1) which classifies DLBCL into germinal center type and non-germinal center type. Cases with CD10 expression by >30% of cells are regarded as GC type as well as cases that are CD10−, BCL6+, IRF4/MUM1−. All other cases are regarded as of non-GC type [25, 62].

**Figure 8** *Diffused large cell lymphoma showing diffuse effacement by large cells.*
