BCL-1 REARRANGEMENT AND CYCLIN D1 PROTEIN EXPRESSION IN MULTIPLE LYMPHOMATOUS POLYPOSIS

Multiple lymphomatous polyposis (MLP), characterized by multiple polyp s involving long segments of the gastrointestinal (GI) tract, is belie ved to represent CI involvement by mantle cell lymphoma (MCL), primari ly based on its histologic and immunophenotypic similarities with MCL. However, rearrangement of the bcl-1 locus, the molecular lesion chara cteristic of MCL, has not been investigated in this group of patients. The authors evaluated the morphologic, immunophenotypic, and molecula r features of 18 cases of MLP and 8 B-cell lymphomas involving the GI tract (including 6 MALT lymphomas). All MLP cases presented with GI di sease, and were histologically similar to MCL. DNA extracted from form alin-fixed, paraffin-embedded tissue was analyzed for evidence of bcl- 1 rearrangement by PCR, using chromosome 11 specific and consensus JH primers. Amplifiable DNA,vas obtained in 24 of 26 cases (16 of 18 MLP cases and 8 of 8 controls). bcl-1 rearrangement was detected in 6 of 1 6 cases (38%), subsequently confirmed by sequencing of the breakpoint region, and in 0 of 8 controls. Immunostaining for cyclin D1 was posit ive in 14 of 18 MLPs, including the 6 bcl-1 rearranged cases and negat ive in 6 of 6 evaluable controls. The detection of bcl-1 rearrangement and cyclin D1 expression in cases of MLP supports the view that MLP r epresents primary MCL of the CI tract. These techniques may also be he lpful in differentiating MLP from other GI lymphomas, particularly low grade lymphomas of MALT, when only small routinely fixed endoscopic b iopsies are available.