Genetic and Immunohistochemical Characterization of Epstein-Barr Virus-Associated Diffuse Large B-Cell Lymphoma

Abstract

Epstein-Barr virus (EBV) has a pathogenic role in several lymphomas, including diffuse large B-cell lymphoma (DLBCL). EBV-associated genetic aberrations in DLBCL have not been fully characterized. The aim of this study was to investigate the prevalence of EBV infection in sporadic DLBCL cases in Kuwait and to evaluate their EBV status in relation to demographic data, the anatomical disease site, immunophenotypic features, particularly pertaining to the Choi's DLBCL prognostic classification, and chromosomal aberrations. Using immunohistochemistry (IHC), in situ hybridization (ISH), nested polymerase chain reaction (nPCR) and comparative genomic hybridization techniques, formalin-fixed paraffin-embedded blocks of archived DLBCL cases were included and evaluated in the study. EBV was detected in 6.9, 18.2 and 25% of the studied cases using IHC, ISH and nPCR, respectively, indicating that nPCR is more sensitive in detecting EBV than IHC and ISH. EBV- DLBCL cases showed BCL6 protein expression more frequently than EBV+ DLBCL cases. The reported prevalence of EBV+ DLBCL cases in this study is similar to that reported in the literature using ISH results and higher using nPCR results. There was a significant inverse correlation between BCL6 protein expression and the presence of EBV (p = 0.01).

The Role of EBV in the Pathogenesis of Diffuse Large B Cell Lymphoma

“…Compared to EBV-negative LPD, patients with EBV-positive tumors had a higher rate of extranodal involvement, a more aggressive clinical course, frequent refractory disease or early relapse, and worse overall survival. Since this initial observation, groups in other countries have confirmed the existence of DLBCL patients with EBV-positive tumors and without known immunodeficiency (Gibson and Hsi 2009;Beltran et al 2011;Hoeller et al 2010;Hofscheier et al 2011;Uner et al 2011;Al-Humood et al 2014). Consistent with the initial report, these EBVpositive immune competent individuals are almost exclusively elderly.…”

“…EBV-positive DLBCLs typically demonstrate an effacement of nodal and extranodal tissue architecture by large, rapidly proliferating immunoblasts with interdispersed areas of geographic necrosis (Al-Humood et al 2014;Oyama et al 2007;Dojcinov et al 2011). The cellular makeup of the tumor is variable, with both polymorphic and monomorphic subtypes described.…”

“…Malignant cells are typically positive for B cell markers CD19, CD20, CD79a, and PAX-5. Ki67, a marker of proliferation, is usually present in greater than 50 % of tumor cells (Swerdlow et al 2008;MontesMoreno et al 2012;Al-Humood et al 2014). Using immunohistochemical markers, post-germinal center (ABC-associated) proteins IRF4, MUM1, are typically positive.…”

“…Cytogenetic and FISH studies in tumors from EBV-positive DLBCL of the elderly have revealed no characteristic abnormalities (Al-Humood et al 2014). Chromosomal translocations involving the heavy chain locus occur in approximately 15 % of samples (Montes-Moreno et al 2012).…”

“…Chromosomal translocations involving the heavy chain locus occur in approximately 15 % of samples (Montes-Moreno et al 2012). Cytogenetic alterations have been reported, including copy number gains of the C-MYC, BCL2, and BCL6 loci (Dojcinov et al 2011). Al-Humood et al (2014 reported that the mean total number of chromosomal alternations per case was less than that seen for EBV-negative disease.…”