T(11-18)(Q21-Q21) IS THE MOST COMMON TRANSLOCATION IN MALT LYMPHOMAS

Background. Low grade malignant lymphomas arising from mucosa associat ed lymphoid tissue (MALT) represent a distinct clinicopathological ent ity. The cytogenetic findings and molecular genetics of MALT lymphomas remain minimally defined. Cytogenetic studies infrequently constitute part of the diagnostic work-up of MALT lymphomas, most commonly due t o small biopsy size and their extranodal localization. Only 28 MALT ca ses with a clonal karyotype have been published to date. A number of c hromosomal abnormalities have been observed with the majority of the c ases featuring trisomy of chromosome 3 which is present in up to 78% o f the cases. Materials and methods. A total of 116 cases of MALT lymph oma were diagnosed at BCCA between 1988 and 1997. Eleven cases of path ologically confirmed MALT lymphomas were subjected to cytogenetic anal ysis at the time of the initial evaluation. Eight of 11 cases yielded successful cultures and the presence of a clonal karyotype using stand ard cytogenetic methodology. In addition, a single case of orbital MAL T lymphoma with a clonal karyotype has been obtained through our consu ltative practice from University of Nebraska Medical Center. These nin e cases of MALT lymphoma with a clonal karyotype are the subject of th is report. Results and conclusion: In this study we report nine cytoge netically studied MALT lymphomas, three of which feature a novel t(11; 18)(q21;q21) translocation which has also been observed in five other MALT cases described in the literature. This recurrent translocation i s the most common translocation associated with MALT lymphomas being p resent in 33% (three of nine) of our cases and 18% (five of 28) of the previously published cases. The results suggest that a potentially im portant gene located at one of these breakpoints may be involved in th e pathogenesis of MALT lymphomas.