Lymphoma

Lymphoma is a group of cancers that arise from lymphocytes, the B cells, T cells and natural killer cells of the immune system. Whereas leukemia mainly fills the bone marrow and blood, lymphoma usually grows as solid masses in lymph nodes and other lymphoid tissue, such as the spleen, tonsils and gut lining, though it can reach almost any organ. The commonest sign is a painless, enlarging lymph node in the neck, armpit or groin, sometimes with B symptoms: fever, drenching night sweats and weight loss.

There are two broad families. Hodgkin lymphoma is defined by large, abnormal Reed-Sternberg cells scattered among many normal immune cells; it often affects young adults and is usually curable. Non-Hodgkin lymphomas form a larger, varied group, mostly of B-cell origin, from slow-growing (indolent) types such as follicular lymphoma, which may simply be monitored, to aggressive ones such as diffuse large B-cell lymphoma, which need prompt treatment. Risk rises with weakened immunity, as in HIV infection or after organ transplantation, and with infections such as Epstein-Barr virus and Helicobacter pylori.

Diagnosis requires a biopsy, ideally of a whole lymph node, with tests of the cells' markers and genes, then scans to stage the disease. Treatment can include chemotherapy, radiation, antibodies such as anti-CD20 drugs, CAR T cells and stem cell transplantation.