Diffuse large B-cell lymphoma is the most common subtype of non-Hodgkin lymphoma (NHL) in adults characterized by a median age of presentation in the sixth decade of life (but also rarely occurring in adolescents and children) with the initial presentation being single or multiple rapidly growing masses (that may or may not be painful) in nodal or extranodal sites (such as thyroid, skin, breast, gastrointestinal tract, testes, bone, or brain) and that can be accompanied by symptoms of fever, night sweats and weight loss. DLBCL has an aggressive disease course, with the elderly having a poorer prognosis than younger patients, and with relapses being common. The disease is MONDO_0018905 (diffuse large B-cell lymphoma). Also known as: DLBCL.