Gastrointestinal Richter's syndrome.

The development of a diffuse large cell lymphoma of the stomach in a patient who had chronic lymphocytic leukemia is reported. Richter's syndrome localized to the gut has not been described previously. Morphologic and immunologic studies suggest that the diffuse large cell lymphoma arose from the same clonal proliferation, IgG lambda, as the initially detected serum monoclonal protein associated with the chronic lymphocytic leukemia.