Prognostic Molecular Features in Diffuse Large B-Cell Lymphoma from Saudi Arabia.

Molecular features that can classify diffuse large B cell lymphoma (DLBCL) in clinically relevant subgroups have recently been demonstrated in studies investigating Western Patients. Different etiologic factors and potentially also varying genetic predispositions have been demonstrated for lymphoma patients from developing countries. To investigate whether proposed molecular classifiers are equally important for Middle East as for Western populations, we analyzed coexpression of CD10/bcl6 (by immunohistochemistry), IgH/Cyclin D1 translocations (by fluorescence in situ hybridization) and methylation of the gene encoding the DNA repair enzyme O⁶ methyguanine -DNA methytransferase gene (MGMT) in a series of 236 DLBCL patients from Saudi Arabia. Clinical follow up data were available from 190 patients. Coexpression of CD10/bcl6 was found in 21%, IgH/Cyclin D1 translocations in 18.3%, and MGMT methylation in 70% of cases. With the exception of MGMT methylation which was reported in only 20–35% of European patients, these numbers were in the range expected from the Western literature. Despite the markedly higher number of MGMT methylation in Saudi cases, its proposed positive effect on DLBCL prognosis could be confirmed (p<0.05). IgH/Cyclin D1 translocations were significantly more frequent in DLBCL with CD10/bcl6 coexpression (12 of 41) than in DLBCL without CD10/bcl6 coexpression (4 of 36; p<0.05). However, neither CD10/bcl6 coexpression nor IgH/Cyclin D1 translocation was related to clinical outcome in our study. In summary, our data do not suggest major molecular differences between Saudi and European DLBCL. Methylation of MGMT gene is a strong prognostic factor in DLBCL. IgH/Cyclin D1 translocations are predominantly found in DLBCL of germinal center (CD10/bcl6 positive).