Extranodal diffuse follicular center lymphoma mimicking mantle cell lymphoma of the intestine

We report a case of diffuse follicular center lymphoma (FCL), which is a morphological variant of follicular lymphoma, resembling multiple lymphomatous polyposis (mantle cell lymphoma of the intestine). The patient was a 48‐year‐old Japanese man who was found, by colonoscopy, to have numerous small polypoid lesions along the entire large intestine. Abdominal computed tomography revealed hepatosplenomegaly and enlargement of multiple mesenteric lymph nodes. Histologically, the lesion was characterized by diffuse proliferation of small‐ to medium‐sized lymphocytes with cleaved nuclei in the mucosa and submucosa. Immunohistochemical studies showed that the tumor cells were CD20+, CD10+, BCL‐2+, CD5–, surface IgM–, and cyclin D1–. Moreover, a cytogenetic study showed a translocation at (14;18)(q32;q21). Finally, this case was diagnosed as diffuse FCL, although the tumor was mimicking mantle cell lymphoma. Am. J. Hematol. 74:287–289, 2003. © 2003 Wiley‐Liss, Inc.