Deletion of sequences telomeric of the EVI1 gene in 3q26 associated with a novel pericentric inv(3)(p25q26) in a patient with acute myelogenous leukemia.

Several recurrent chromosome rearrangements affecting the EVI1 locus in chromosome band 3q26 have been described in myeloid leukemia. They lead either to overexpression of this oncogene, or to the formation of EVI1 fusion transcripts.1 We employed two separate split-signal interphase fluorescent in situ hybridization (FISH) assays that facilitate the detection of 3q26 and of 3q21 rearrangements2,3 (Figure 1A) to screen myeloid leukemia samples submitted to our laboratory for cytogenetic analysis. In the bone marrow of a 58 year old male patient suffering from acute myeloid leukemia (FAB subtype: AML M1; white blood cell count at presentation, 49.5×109/L with 84% blasts, hemoglobin 9.1g/dL, platelet count 53×109/L), we found aberrant signal patterns with the 3q26 assay, but not with the 3q21 assay. G-band analysis revealed monosomy 7 as the sole cytogenetic anomaly, and FISH with a whole chromosome paint did not give any indication of a chromosome 3 rearrangement. Analysis of metaphases hybridized with the 3q26 interphase FISH probe revealed that the red and the green signals, which are located centromeric and telomeric, respectively, of typical 3q26 breakpoints (Figure 1A) appeared at the opposite ends of the rearranged chromosome 3. This indicated the presence of a not previously described pericentric inversion of chromosome 3, inv(3)(p25q26) (see http://cgap.nci.nih.gov/ Chromosomes/Mitelman). This inversion was somatically acquired, because it was not present in any of over 100 metaphases of PHA-stimulated peripheral blood leukocytes.