Lymphoma Types, Symptoms, Prognosis, Treatment, Stages & Survival Rates: Lymphoma Overview Lymphoma is a type of cancer involving cells of the immune system, called lymphocytes. Just as cancer represents many different diseases, lymphoma represents many different cancers of lymphocytes — about 35 different subtypes, in fact. Lymphoma is a group of cancers that affect the cells that play a role in the immune system and primarily represents [...]