RUNX1 deletion/amplification in therapy-related acute myeloid leukemia: A case report and review of the literature.

Intrachromosomal amplification of chromosome 21 (iAMP21) is a rare occurrence in acute myeloid leukemia (AML). We describe here a case of AML with apparent amplification of RUNX1 by cytogenetics and FISH. A 39-year-old female in remission from stage IIIa breast cancer was diagnosed with therapy-related AML (t-AML). The patient's bone marrow was hypocellular for her age (30-40%) with 25% blasts. Cytogenetic analyses revealed a complex karyotype, characterized by rearrangements in chromosomes 1, 5, 17, 20, an additional unidentified marker chromosome, and apparent amplification of chromosome 21. Fluorescence in situ hybridization detected deletions of CKS1B, EGR1, TP53, and apparent amplification of RUNX1 (6-8 signals). Array comparative genomic hybridization (array-CGH) detected amplification of the 5' non-coding region of RUNX1 and deletion of the 3' coding region of RUNX1. These results show that this is not a true case of iAMP21 and suggest that RUNX1 is not the primary target of amplification.