الفهرس 
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Abstract
Diffuse large B-cell lymphoma (DLBCL) is the most common type of lymphoma, accounting for 30-40% of adult non-Hodgkin lymphoma worldwide. Diffuse large B-cell, not otherwise specified (DLBCL, NOS) represents 80-85% of DLBCL cases (Onaindia et al., 2021).
In Egypt, diffuse large B cell lymphoma (DLBCL) is the most common subtype of Non-Hodgkin lymphoma (NHL) in Egypt. It represents about 44.8% and 50.1% of total NHL cases according to the latest registries of Ain Shams University Hospitals and the National Cancer Institute of Cairo University, respectively (Helal et al., 2015); (Mokhtar et al., 2016).
Cell of origin (COO) subclassification of DLBCL, NOS cases into the germinal center B-cell subtype (GCB) and the activated B-cell subtype (ABC) is important and continues to be acknowledged by the World Health Organization (WHO) as fundamentally different genetic profile and biological behavior characterizes each subtype. Therefore, DLBCL, NOS subtypes- GCB and ABC- are associated with different survival outcomes.
The aim of the current work is to study and gain insight into the pathological and demographic data of the subtypes of diffuse large B-Cell lymphoma, NOS cases in Egyptian patients diagnosed in Ain Shams University Hospitals during the years from 2020 to 2022.
In the study, we recorded 132 cases of DLBCL, NOS diagnosed in Ain Shams University Hospitals during this period. According to Hans and Modified Hans immune algorithms, 102 cases were further subclassified into 39 cases of GCB subtype and 63 cases of ABC subtype. Thirty cases were not subtyped further due to unavailability of the paraffin blocks or tissue block consumption.
DLBCL, NOS represented 35.3 % of all NHL cases and 26.19% of all lymphoma cases overall. Moreover, the GCB subtype cases represented 38.2% of DLBCL, NOS cases whereas, the ABC subtype cases represented 61.8 %.
Later, we compared between the GCB and ABC subtypes regarding the demographic and pathological data.
The mean age for DLBCL, NOS was 54.9 ± 12.75 with male to female ratio of 1.3:1. The ABC subtype showed a higher mean age (55.49 ± 11.96) with female affection predominance as compared to the GCB subtype (mean age= 53 ± 12.87).
The most affected site was the cervical nodal group. Whereas, the stomach, spleen and liver were reported as the most commonly involved extranodal sites. The ABC subtype showed more nodal involvement with significant association with extra-abdominal nodal groups as compared to the GCB subtype (P= 0.02).
The mean Ki-67 proliferation index for DLBCL, NOS was 70.42 ± 14.03. A higher proportion of the ABC subtype cases reported higher Ki-67 index > 70% with a mean of 74.21 ± 14.51 as compared to the GCB subtype cases with a mean of 69.1 ± 13.76 (P=0.08).
Tumor necrosis was noted in 34.8% of DLBCL, NOS cases with higher incidence of occurrence in cases belonging to the ABC subtype than the GCB subtype (P=0.45). Moreover, centroblastic morphological variant was the most common histology reported in both subtypes. Whereas, less common histological variants- immunoblastic and anaplastic variants- were encountered more in the ABC subtype.
In summary, the incidence of DLBCL, NOS in Ain Shams University Hospitals was closely similar to the recorded international incidence. According to COO, the ABC subtype was more frequent than the GCB subtype in the current study. The ABC subtype was associated with more nodal involvement with a significant predilection to extra-abdominal nodal groups. Compared to the GCB subtype, the ABC subtype showed more aggressive histopathological features as higher ki-67 proliferation index, the presence of necrosis, and the occurrence of advanced histological immunoblastic and anaplastic variants.