TRAF3 has been proposed as a tumor suppressor protein since a number of biallelic deletions or inactivating mutations has been identified in human B cell malignancies, including B-chronic lymphocytic leukemia (CLL), splenic marginal zone lymphoma (SMZL), mantle cell lymphoma, diffuse large B-cell lymphoma (DLBCL), and multiple myeloma (MM), as well as in Waldenström's macroglobulinemia (21–27). This evidence concerns the gene TRAF3 and splenic marginal zone lymphoma.