FLUORESCENCE IN-SITU HYBRIDIZATION ANALYSIS OF WHOLE-ARM 7-12-TRANSLOCATIONS IN HEMATOLOGIC MALIGNANCIES

Cytogenetic analysis of one case of acute myeloid leukemia (AML), one of acute lymphoblastic leukemia (ALL), one of refractory anemia with e xcess of blasts (RAEB), and one of acute mixed lineage leukemia (AMLL) with unbalanced 7;12 translocations mapped the breakpoints to the cen tromeres on both chromosomes. The rearrangements were interpreted as t he whole-arm translocations der(7;12)(q10;q10) in the AML and ALL and der(7;12)(p10;q10) in the RAEB and AMLL, However, further analysis by metaphase and/or interphase fluorescence in situ hybridization (FISH) showed centric fusion only in the AML and ALL In the RAEB and AMLL, ce ntromeric material from chromosome 7 but nor from 12 was present in th e derivative chromosome. Whereas the t(7;12) resulted in loss of 12p i n all four cases, the corresponding chromosome 7 imbalances differed-m onosomy for 7q in the RAEB and AMLL and monosomy for 7p in the AML and ALL. Six hematologic neoplasms with unbalanced whole-arm or near-cent romeric 7;12 translocations and seven dic(7;12) with juxtacentromeric breakpoints have been reported previously: 2 AML, I RAEB in transforma tion, and IO ALL. All karyotypically informative cases had loss of 12p material. All bur one of the cases with combined 7p and 12p deletion were ALL, whereas all cases with 7q and 12p loss showed myeloid differ entiation. No particular clinical, morphologic, or immunophenotypic fe atures seem to characterize ALLs with t(7;12). AMLs with an unbalanced t(7; 12), often together with 5q deletions, might be associated with previous genotoxic exposure and poor prognosis. (C) 1995 Wiley-Liss, I nc.