A novel case of intrachromosomal amplification and insertion of RUNX1 on derivative chromosome 2 in pediatric AML.

Intrachromosomal amplification of RUNX1 gene on chromosome 21 (iAMP21) is a rare occurrence in acute myeloid leukemia (AML). Herein, we describe a case of AML with amplification of RUNX1 and its insertion on chromosome 2 detected by conventional karyotyping and confirmed by metaphase FISH. A six-year-old female was diagnosed as acute myeloid leukemia with monocytic differentiation. The patient's bone marrow revealed 74% blasts which were MPO negative. Conventional karyotyping revealed a complex karyotype, with rearrangements in chromosomes 1, 2, 7, 8 and hsr(21). FISH on interphase cells with LSI RUNX1-RUNX1T1 dual colour dual fusion translocation probe showed 6-7 copies of RUNX1 signal. Metaphase FISH with LSI RUNX1-RUNX1T1 probe confirmed amplification of RUNX1 and insertion of amplified RUNX1 sequences on long arm of chromosome 2. Induction chemotherapy was initiated, however, the patient died within one month of diagnosis suggesting poor outcome associated with this novel finding. Insertion of amplified RUNX1 on another chromosome has not yet been reported so far.