Immunohistochemical subtyping of diffuse large B-cell lymphoma into germinal center B-cell and activated B-cell subtype, along with correlation of the subtypes with extranodal involvement, serum lactate dehydrogenase, and positron emission tomography scan-based response assessment to chemotherapy

Abstract

Context: Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma in Indian population and is divided into the prognostically important subtypes, germinal center B-cell (GCB) and activated B-cell-like (ABC), using immunohistochemistry-based algorithm.

Aim: The present study aims to evaluate the influence of immunohistochemical derived DLBCL subtype, GCB or ABC on prognostically significant variables - extranodal involvement and serum lactate dehydrogenase (LDH) level at presentation, and response to chemotherapy assessed on pre- and posttreatment fluorodeoxyglucose-positron emission tomography study.

Settings and design: This was a retro-prospective, 2-year observational study at a tertiary health-care center, New Delhi.

Subjects and methods: The study population includes a total 236 cases of DLBCL. According to the Hans algorithm, DLBCL cases were allocated to the GCB and ABC subgroups.

Statistical analysis used: For comparison of mean values, independent t-test and analysis of variance were used. For this purpose, we used SPSS 20.0 software. P < 0.05 was considered as statistically significant.

Results: Ninety-eight patients (41.5%) had GCB immunophenotype and 138 patients (58.5%) were ABC. A significant difference was observed between mean baseline level of LDH between GCB and ABC subtypes (P < 0.05). The proportion of cases with extranodal involvement was comparatively higher in ABC subtype (P < 0.05). Association between response to chemotherapy with DLBCL immunophenotypes was found to be highly significant (P < 0.00). The response rates were much better in GCB subtype.

Conclusions: The mean baseline level of LDH is significantly higher in ABC subtype. The proportion of cases with extranodal involvement was comparatively higher in ABC and shows poor response to chemotherapy as compared to GCB. Baseline LDH level was found to be important prognostic marker in the DLBCL.

Keywords: Diffuse large B-cell lymphoma; Hans algorithm; immunophenotype.