Diffuse large B-cell lymphoma (DLBCL) is a cancer of B cells, a type of lymphocyte that is responsible for producing antibodies. It is the most common form of non-Hodgkin lymphoma among adults, with an annual incidence of 7–8 cases per 100,000 people per year in the US and UK. This cancer occurs primarily in older individuals, with a median age of diagnosis at ~70 years, although it can occur in young adults and, in rare cases, children. DLBCL can arise in virtually any part of the body and, depending on various factors, is often a very aggressive malignancy. The first sign of this illness is typically the observation of a rapidly growing mass or tissue infiltration that is sometimes associated with systemic B symptoms, e.g. fever, weight loss, and night sweats.The causes of diffuse large B-cell lymphoma are not well understood. Usually DLBCL arises from normal B cells, but it can also represent a malignant transformation of other types of lymphoma (particularly marginal zone lymphomas) or, in rare cases termed Richters transformation, chronic lymphocytic leukemia. An underlying immunodeficiency is a significant risk factor for development of the disease. Infections with the Epstein–Barr virus (EBV), Kaposis sarcoma-associated herpesvirus, human immunodeficiency virus (i.e. HIV), and the Helicobacter pylori bacterium  are also associated with the development of certain subtypes of diffuse large B-cell lymphoma.
Subtypes of diffuse large B-cell lymphoma
DLBCL subtypes have been sorted into groups based on their distinctive morphology or immunophenotype, distinctive clinical issues, and distinctive virus-driven etiology. The prognoses and treatment of these subtypes varies with their severity. Most subtypes are aggressive diseases and consequently treated in a manner similar to DLBCL,NOS. Further details on these subtypes, including their treatments, can be found in their respective main article linkages. DLBCL with a distinctive morphology or immunophenotype
T cell/histiocyte-rich large B-cell lymphoma
T-cell/histiocyte-rich large B-cell lymphoma (THRLBCL) is a DLBCL in which tumors containing small numbers of usually large neoplastic B-cells embedded in a background of reactive T-cells and histiocytes develop in the liver, spleen, bone marrow and/or, rarely other sites. Patients usually present with advanced disease; their overall 3 year survival rates in different studies range between 46% and 72%. ALK+ large B-cell lymphoma
ALK+ large B-cell lymphoma (ALK+ LBCL) is a DLBCL in which neoplastic lymphocytes that express the ALK tyrosine kinase receptor protein infiltrate lymph nodes as well as extranodal sites, e.g. the mediastinum, bones, bone marrow, nasopharynx, tongue, stomach, liver, spleen, and skin. About 60% of these individuals present with advanced disease. ALK+ LBCL has an overall 5 year survival rate of ~34%. Plasmablastic lymphoma
Plasmablastic lymphoma (PBL) is a DLBCL in which neoplastic immunoblastic or plasmablastic cells embedded in a background of other cell types infiltrate the oral/nasal cavity or much less often the gastrointestinal tract. Some 70% of individuals with PBL are infected with EBV and/or (particularly those with oral/nasal cavity disease) human immunodeficiency virus (HIV).