any of a group of malignant diseases of the lymphatic system usually starting in the lymph nodes (lymph node) or in lymphoid tissues of other organs, such as the lungs, spleen, and skin. Lymphomas are generally classified into two types, Hodgkin disease and non-Hodgkin lymphoma.

Hodgkin disease results in enlargement of the lymph nodes and spleen. Whereas Hodgkin disease generally has a high cure rate, non-Hodgkin lymphomas are often more difficult to treat. Burkitt lymphoma is a non-Hodgkin type that is most commonly found in African children; research suggests it may be linked in some way to the Epstein-Barr virus. Other non-Hodgkin lymphomas are referred to in a number of ways that describe the morphology of the cells and whether the tumours are diffuse or nodular. Generally speaking, the nodular type of disease progresses more slowly than the diffuse type. Diffuse large-cell lymphomas are more aggressive and are able to involve the liver, lungs, kidneys, and even the brain. Some lymphomas invade the bloodstream, causing leukemia. Diagnosis of either major form of lymphoma requires laboratory analysis of tissue, usually from the lymph nodes.