NEW SUBTYPE OF PRE-B ACUTE LYMPHOBLASTIC-LEUKEMIA WITH T(5-12)(Q31Q33-P12), MOLECULARLY AND CYTOGENETICALLY DISTINCT FROM T(5-12) IN CHRONIC MYELOMONOCYTIC LEUKEMIA

Translocation t(5;12)(q33;p13), resulting in an ETV6/PDGFRB gene fusio n, is a recurrent chromosomal abnormality associated with chronic myel omonocytic leukemia (CMML). An analogous translocation was also found in four cell lines with features of pre-B acute lymphoblastic leukemia (ALL). Using fluorescence in situ hybridization (FISH) we show here t hat in three of these cell lines identical complex rearrangements occu rred. However, the regions involved on 5q and 12p are different from t he breakpoints in CMML, and the translocation is accompanied by seemin gly identical cryptic deletions of both 5q and 12p chromosome sequence s in all analyzed pre-B ALL cell lines. The similar cytogenetic, FISH, and immunophenotyping findings in the three cell lines suggest that t he t(5;12)(q31q33;p12) defines a new entity of preB ALL. (C) 1997 by T he American Society of Hematology.