CONSISTENT COPY NUMBER GAIN IN CHROMOSOME-12 IN PRIMARY DIFFUSE LARGE-CELL LYMPHOMAS OF THE STOMACH

Fifteen cases of high grade primary gastric non-Hodgkin's lymphomas we re studied using comparative genomic hybridization (CGH) and/or fluore scence irt situ hybridization (FISH) techniques. A total of 10 cases o f diffuse large cell lymphoma (DLCL) with no histologically identifiab le or previous history of low grade mucosa-associated lymphoid tissue (MALT) lymphoma components were examined, four by CGH and validated by FISH, and the remaining six by FISH alone. All 10 tumors showed gains in chromosome 12. Other recurring CGH findings in DLCL included copy number gains of 1q and deletions of 6q. Five cases of high grade tumor s with low grade MALT components (HGM) were also examined, three by CG H and validated by FISH and two by FISH only. Only one in five HGM sho wed gains of chromosome 12. Other recurring CGH findings in HGM includ ed +7q and +11q. We conclude that high grade gastric lymphomas of DLCL type were associated with gains in chromosome 12. The change was much less frequent (P < 0.01) in the HGM type, which had a percentage simi lar to that observed in previously reported cytogenetics/FISH studies on low grade MALT lymphomas. Our findings suggested that many DLCL wer e not derived from transformation of low grade MALT lymphomas.