Colonic primary large cell lymphoma with marginal zone growth pattern presenting as multiple polyps

We report a rare case of primary gastrointestinal lymphoma, stage IE, in a 58-year-old white man who had multiple colonic polyps measuring up to 1 x 1 .1 cm. The tumor originated in the marginal zone of the follicles infiltrat ing the interfollicular spaces. Follicular colonization was frequently seen . The mucosa was spared by the infiltrate. Morphologically, the neoplastic cells were monomorph, intermediate-sized blasts. Rare small to intermediate sized cells, some with centrocyte-like morphology, intermingled the blasti c infiltrate. The neoplastic cells expressed CD20 and had a monotypic immun oglobulin of cytoplasmic IgM (kappa) on paraffin sections. Tumor cells stai ned negative for CD45RO, CD5, CD10, IgD, and CD23. Polymerase chain reactio n revealed a clonal V-D-J rearrangement. Bcl-1 and bcl-2 rearrangement were not detected. We therefore suggest the diagnosis of primary large cell lym phoma with marginal zone growth pattern mimicking colonic adenomas.