MULTIPLE LYMPHOMATOUS POLYPOSIS OF THE GASTROINTESTINAL-TRACT - AN EXTENSIVE HISTOPATHOLOGIC AND IMMUNOHISTOCHEMICAL STUDY OF 12 CASES

Background. Multiple lymphomatous polyposis (LP) is a rare entity, cha racterized by multiple polypoid tumors involving several segments of t he gastrointestinal tract. Methods. In this large retrospective series of 12 patients with LP, histologic and immunohistochemical features w ere investigated from patients with multiple biopsy samples from each site (500 gastrointestinal biopsies). Immunohistochemistry was perform ed on paraffin embedded biopsies from 12 patients and on frozen tissue biopsies from 8 patients, for each of whom at least two different ana tomic sites were studied. Results. Histologic features always were cha racterized by nodules located in mucosa and submucosa composed of lymp homatous, small cleaved cells. B-cell phenotype of the neoplastic cell s was the same phenotype as adult mantle-zone cells or fetal follicle cells (frequent coexpression of surface IgM and surface IgD, and weak expression of CD5, CD35+, CDw32+, and CD23-). Tested cases expressed b cl-2. Five to 20% of LP cells were positive for the monoclonal antibod y Ki-67. Five patients died within 5-32 months after diagnosis. Freque nt extradigestive sites were also identified. There were two unique fi ndings: five cases with digestive tract lymphoepithelial lesions (LEL) , and one secondary transformation to large B-cell malignant lymphoma. Conclusions. To the authors' knowledge, this is the largest series so far of LP studied with immunohistochemistry on frozen sections. Mantl e-cell B cell phenotype of the nodular monotonous, small cleaved cells is confirmed. This entity may be classified as mantle-cell lymphoma w ith a similar agressive clinical course, and treated as a high grade B -cell lymphoma. The authors know of no such LEL that has been reported previously, and secondary transformation has been described only brie fly in one case.