Lymphoma is a general term for a variety of cancer that begins in the lymphatic system. In technical terms, lymphoma denotes malignancies of lymphocytes or, more rarely, of histiocytes. Collectively, these cell types form the reticuloendothelial system and circulate in the vessels of the lymphatic system. Just as there are many types of lymphocytes, so there are many types of lymphoma.
Traditionally, Lymphoma is classified as Hodgkin's lymphoma, discovered by Thomas Hodgkin in 1832, and non-Hodgkin's lymphoma (all other types of lymphoma). Modern classifications of lymphoma have moved away from this artificial division.