Mantle cell lymphoma (MCL) frequently comes up in the discussion of CLL because its clinical presentation is extremely similar to that of CLL. Enlarged liver and spleen (hepatosplenomegaly) and elevated lymphocyte counts (lymphocytosis) are common in both diseases. However, MCL is a non-Hodgkin's lymphoma, which has its origins in the lymph nodes, whereas CLL is a leukemia and has its origins in the bone marrow.

Flow cytometry results of MCL are very similar to those of CLL. CLL lymphocytes co-express B-cell antigens CD19 and CD20 along with the T-cell antigen CD5. With the exception of SLL, MCL is the only disease that also expresses these antigens. However, CLL lymphocytes also express CD23; whereas, MCL lymphocytes do not. This lack of expression of CD23 is useful in distinguishing MCL from CLL. In addition, the antigen density of CD20 is typically much lower in CLL than it is in MCL. This is one of the reasons why rituxan, the anti-CD20 monoclonal antibody, is more effective in the treatment of lymphoma than it is in CLL. For more information on CD markers and flow cytometry see, What is flow cytometry?

MCL is also known as small-cleaved lymphoma, intermediate differentiation lymphoma, centrocytic lymphoma, and mantle zone lymphoma, but it should not be confused with marginal zone lymphoma. MCL comprises approximately 5 percent of all non-Hodgkin's lymphomas. The median age at diagnosis is approximately 55 years and approximately 80 percent of patients are males. Three subtypes of MCL have been noted: Nodular MCL, Diffuse MCL and Blastic MCL. MCL, like CLL, is currently considered incurable.