A Rare Case of Waldenstrom Macroglobulinemia of the Rectosigmoid Colon

Abstract

Waldenstrom macroglobulinemia is an uncommon mature B-cell lymphoma characterized by monoclonal immunoglobulin M protein in peripheral blood and lymphoplasmacytic cells in bone marrow and/or extramedullary sites. The gastrointestinal tract is a rare site of involvement. The diagnosis is based on clinicopathologic findings, although somatic mutations, such as MYD88, can aid in the diagnosis. We present a patient with irregular stools diagnosed with Waldenstrom macroglobulinemia involving the rectosigmoid colon by histopathology and immunohistochemistry on colonic biopsies, immunoglobulin M protein in serum, clonal plasma cells in bone marrow, and MYD88 mutation in colonic and bone marrow specimens.

Figure 1.

Colonoscopy showing a localized segment of rectosigmoid colitis characterized by moderate edema, friability, erosions, and erythema.

Figure 2.

Repeat colonoscopy showing congested mucosa in the rectosigmoid colon, similar to the initial examiantion.

Figure 3.

Endoscopic ultrasound showing diffuse mass-like wall thickening with hypoechoic extension through all 5 echo layers in the rectosigmoid colon and multiple small, hypoechoic perirectal lymph nodes.

Figure 4.

The infiltrating cells were positive for B-cell markers CD20/PAX5, and the CD138 positive plasma cells were notable for kappa light chain restriction.