2.4. Morphology

Under light microscopy, the normal architecture of lymph nodes is completely effaced by the sheets of atypical lymphoid cells. The tumor cells resemble normal centroblasts or immunoblasts with nuclei size at least twice the size of a small lymphocyte. While the centroblasts are large,

Figure 1. Lymph node sections showing GC type DLBCL (a) The H&E stained sections of lymph node showing diffuse infiltration of atypical lymphoid cells that are large in size with irregular nuclear contours, vesicular chromatin, and some with prominent nucleoli (X10 and X40 magnification). (b) On immunohistochemistry, CD20 highlights the infiltrating cells (X20 magnification) (c) cells are negative for MUM1 (major subset) (X20 magnification).

noncleaved cells, with round to oval nuclei with multiple nucleoli and thin rim of basophilic cytoplasm, the immunoblasts are larger cells with more prominent nucleoli and abundant cytoplasm. Other less common cytological variants include multilobated and anaplastic forms. However the clinical significance of less common forms is debatable. Due to inter- and intra-observer variability in the characterization of DLBCL based on the appearance of tumor cells, all the morphological subtypes are grouped as one category in the current WHO classification except for plasmablastic lymphoma. The plasmablastic lymphoma displays immunophenotype characteristics which allows its distinction from other morphological subtypes of DLBCL (Figures 1–3).

Histopathological and immunohistochemistry slides of diffuse large B cell Lymphoma showing characteristics of DLBCL of germinal center origin (GC) in Figure 1 and activated B cell origin (ABC) in Figure 2.
