Malignant lymphoma of the transverse colon associated with macroglobulinemia.

We present an unusual case of a malignant lymphoma of the transverse colon associated with macroglobulinemia. A 73-yr-old man was incidentally discovered to have high serum gamma-globulin on a regular check-up. Serum immunoquantitation revealed an IgM level of 3490 mg/dl. Kappa-type Bence-Jones protein was positive in the urine. Immunoelectrophoresis identified the abnormal protein as IgM-kappa. After hospitalization an abdominal tumor was detected with barium and CT, identified as a tumor of the transverse colon. Partial resection of the transverse colon was carried out. Histopathologically the tumor were confirmed as small lymphocytic non-Hodgkin lymphoma of B-cell origin, based on the Working Formulation. According to flowcytometric analysis, the tumor cells were positive for IgM-kappa. The lymphoma cells produced monoclonal IgM, giving rise to macroglobulinemia.