REARRANGEMENT OF PROXIMAL 11Q13 BAND IN A CMML IN ACUTE TRANSFORMATION

Fluorescence in situ hybridization (FISH) was performed on bone marrow cells thought to contain a t(7;11)(p22;q13) from a patient with chron ic myelomonocytic leukemia in transformation. FISH analysis using a pa nel of 10 probes previously mapped to 11q13 revealed a cytogenetically undetected complex rearrangement that involved chromosomes 7 and 11 a s well as a chromosome 3 at band p24. Two distinct translocation break points, both proximal to the BCL1 locus, were found in chromosome 11 t hat perforce separate it into three subregions. The two breakpoints ap pear distinct from the two previously described ones which involved th e FAU and GSTP1 genes. Our observations add to the involvement of prox imal 11q13 in myeloid malignancies.