In EBV+ DLBCL, small neoplastic B-cells, other lymphocyte typess, plasma cells, histiocytes and epithelioid cells interspersed with Reed–Sternberg-like cells infiltrate, almost exclusively, lymph nodes. Elderly patients with the disease have median survival times of ~2 years while young patients have long-term treatment-related remissions in >80% of cases. HHV8-positive diffuse large B-cell lymphoma, NOS
HHV8-positive diffuse large B-cell lymphoma, NOS (HHV8+ DLBCL, NOS; also termed HHV8-positive diffuse large B-cell lymphoma [HHV8+ DLBCL]) is a DLBCL in which Kaposis sarcoma-associated herpesvirus-infected, medium- to large-size neoplastic B-cells that resemble lymphocytes or immunoblasts infiltrate lymph nodes (~80% of cases) and, when disseminated (20% of cases), the liver and spleen. This infiltration usually disrupts the normal architecture of the involved tissues. HHV8+ DLBCL develops in HIV-infected individuals in ~50% of cases, in individuals with multicentric Castleman disease, plasma cell variant in uncommon cases, and in individuals with Kaposi sarcoma in rare cases. HHV8+ DLBCL commonly takes an aggressive course and has a poor prognosis. Related disorders
Helicobactor pylori associated diffuse large B-cell lymphoma
Rare cases of DLBCL are associated with the presence of the bacterium, Helicobacter pylori, in the neoplastic B-cells. While the histology of Helicobactor pylori-associated diffuse large B-cell lymphoma (H. pylori+ DLBCL) is typical of DLBCL, the disease is sometimes a progression of mantle cell lymphoma, is often restricted to the stomach, is less aggressive that most DLBCL cases, and may respond to a drug regimen consisting of antibiotics and proton pump inhibitors directed at killing the bacterium.
Diagnosis
Microscopic examinations of involved tissues reveal large neoplastic cells that are typically classified as B-cells based on their expression of B-cell marker proteins (e.g. CD20, CD19, CD22, CD79, PAX5, BOB1, OCT2, an immunoglobulin [usually IgM but occasionally IgG or IgA)], CD30, and in ~20–25% of cases PD-L1 or PD-L2 (PD-L1 and PD-L2 are transmembrane proteins that normally function to suppress attack by the immune system). These cells arrange in a diffuse pattern, efface the tissues architecture, and resemble Centroblast cells (80% of cases), Immunoblast cells (8–10% of cases), or anaplastic cells (9% of cases; anaplastic cells have bizarre nuclei and other features that may mimic the Reed–Sternberg cells of Hodgkin disease or the neoplastic cells of anaplastic large cell lymphoma). Rarely, these neoplastic cells are characterized as having signet ring or spindle shaped nuclei, prominent cytoplasmic granules, multiple microvillus projections, or, when viewed by electron microscopy, tight junctions with other cells. These neoplastic tissue infiltrates are often accompanied by small non-malignant T-cell lymphocytes and histiocytes that have a reactive morphology. Variants of DLBCL, NOS
The World Health Organization, 2016, requires that the neoplastic cells in DLBCL, NOS be further defined based on whether they are derived from germinal center B-cells (i.e. GBC) or activated B-cells (i.e. ABC) as identified by gene expression profiling (GEP) or are GBC or non-GBC as identified by immunohistochemical (IHC) analyses. As identified by GEP, which measures all cellular messenger RNAs, GBC and ABC represent about 50 and ~35% of DLBCL, NOS cases, respectively, with ~15% of cases being unclassifiable.