TRISOMY-3 IN MARGINAL ZONE B-CELL LYMPHOMA - A STUDY BASED ON CYTOGENETIC ANALYSIS AND FLUORESCENCE IN-SITU HYBRIDIZATION

Trisomy 3 represents the most frequent and consistent chromosomal abno rmality characterizing the recently defined entity marginal zone B-cel l lymphoma (MZBCL). By cytogenetic analysis and/or fluorescence in sit u hybridization (FISH) on interphase nuclei we found an increased copy number of chromosome 3 in 22/36 (61%) successfully analysed cases, in cluding 8/12 cases with extranodal MZBCL, 8/13 cases with nodal MZBCL, and 6/11 patients with splenic MZBCL. Sensitivity of interphase cytog enetics was somewhat higher than that of conventional cytogenetic inve stigation, Structural chromosomal changes involving at least one chrom osome 3 were seen in 11/20 cases with an increased copy number of chro mosome 3: +del(3)(p13) was demonstrated in three cases, and was the so le chromosomal abnormality in one of them: +i(3)(q10) was seen in two other patients; and rearrangements involving various breakpoints on th e long arm of chromosome 3 were found in the remaining cases, FISH on metaphase spreads confirmed these structural abnormalities and additio nally showed two unexpected translocations involving chromosome 3, We conclude that: (1) trisomy 3 occurs in a high proportion of extranodal , nodal and splenic MZBCL; (2) FISH on interphase nuclei is an additio nal and sensitive tool in detecting an increased copy number of chromo some 3 in MZBCL; (3) additional structural abnormalities involving the long arm of chromosome 3 are frequent but non-recurrent and are perha ps secondary changes; and (4) abnormalities such as +del(3)(p13) and i(3)(q10) suggest that genes located on the long arm of chromosome 3 a re of particular importance in the pathogenesis of MZBCL.