LOW NUMBER OF BRA COPY NUMBER CHANGES IN SMALL LYMPHOCYTIC LYMPHOMA

Background and Objective. Small lymphocytic lymphoma (SLL) is morpholo gically and immunological ly similar to chronic lymphocytic leukemia ( CLL), and the new REAL classification refers to them as a single disea se termed SLL/CLL. Recently, frequent losses in 6q, 11q and/or 13q wer e observed in CLL using comparative genomic hybridization (CGH).(1) We performed CGH analyses in order to find out whether these two entitie s contain the same DNA copy number changes. Design and Methods. Sevent een patients with stage IV disease and one with stage III disease were studied by CGH. CGH is based on quantitation of the fluorescence inte nsity of differentially labeled DNAs. For this purpose tumor DNA label ed with FITC-12dUTP and normal DNA labeled with texas red-5dUTF were h ybridized to normal metaphase chromosomes. the ratio of fluorescence i ntensity of hybridized tumor and normal DNA was measured using compute rized image microscopy to identify over- or under-represented regions in the tumor genome. All findings were confirmed using a confidence in terval of 99% with a 1% error probability. Results. The most consisten t finding was a gain of the entire chromosome 12 observed in three pat ients and a loss in 14q24 in one patient. No other changes were detect ed. All abnormal cases presented with stage IV disease and had bone ma rrow infiltration. Two 12+ cases had a leukemic disease. Interpretatio n and Conclusions. Our results indicate that trisomy 12 is one of the most frequent chromosomal aberrations in SLL. Losses regarded as typic al of CLL were not present in SLL. This may indicate that the genetic pathways in the development of SLL/CLL in patients presenting with enl arged lymph nodes (SLL) with or without leukemia are different from th ose in patients presenting with leukemia (CLL) without enlarged lymph nodes. (C) 1998, Ferrata Storti Foundation.