OBJECTIVETo detect specific chromosome rearrangements in acute myeloid leukemia (AML) using interphase-fluorescence in situ hybridization (FISH).

METHODSAll cases were studied by R-band karyotypic analysis using direct method and/or short-term culture for chromosomes preparation. Interphase-FISH was performed in 108 cases of AML with M5, M4, M2, M3 subtypes including 103 cases with normal karyotypes, 4 cases with chromosomal abnormalities other than specific chromosomal rearrangements using chromosome translocation probe such as AML1/ETO, PML/RARα, CBFβ/MYH11 and MLL.

RESULTSOf 38 cases of M2-AML without t(8;21) on conventional cytogenetics(CC) analysis, 4 cases showed positivity for AML1/ETO fusion transcript, which included 2 cases with typical signal model and 2 with insertion. Of 9 cases of M3-AML without t(15;17) on CC analysis, 6 showed positivity for PML/RARα fusion transcript including 2 with typical signal model, 3 with insertion, one without PML/RARα rearrangement on reverse transcription-PCR and FISH assay using PML/RARα probe. FISH assay using the RARα dual color, break-apart rearrangement probe indicated a partial deletion of RARα. Of 23 cases with M4 or M4EO-AML without inv(16) on CC analysis, 3 showed positivity for CBFβ/MYH11 fusion transcript. Of 38 cases without 11q23 translocation on CC analysis, all cases were negative for MLL rearrangement.

CONCLUSIONInterphase-FISH can detect specific chromosome rearrangements such as AML1/ETO, PML/RARα or CBFβ/MYH11 in some AML cases with normal karyotype, though it seemed less useful for the detection of MLL rearrangement.