<bold><italic>MYC</italic></bold> Amplification in the Form of Ring Chromosomes 8 in Acute Myeloid Leukemia with t(11;16)(q13;p11.2).

Oncogene amplification is uncommon in acute myeloid leukemia (AML). Cytogenetically, it is primarily found as double minute chromosomes (dmin) or homogeneously staining regions (hsr). A 62-year-old woman was admitted to our hospital because of anemia and thrombocytopenia. Her bone marrow was hypercellular with 78.6% myeloperoxidase- positive blasts. Some had micronuclei. The patient was diagnosed with AML M2 and remains in complete remission (CR) after induction therapy. G-banding at diagnosis showed 51,XX,t(11;16)(q13;p11.2),+r1,+mar1×4. Spectral karyotyping confirmed t(11;16) and revealed that the ring and the marker chromosomes were derived from multiple copies of ring chromosome 8. Fluorescence in situ hybridization (FISH) with a <italic>MYC</italic> probe at 8q24 detected amplified <italic>MYC </italic>signals on 1 large and 4 small ring chromosomes 8. One <italic>MYC</italic> signal was deleted from one of the 2 chromosomes 8. FISH with a <italic>FUS</italic> probe at 16p11.2 showed monoallelic deletion of <italic>FUS</italic>. Immunohistochemistry demonstrated MYC protein overexpression at diagnosis and almost negative expression in CR. These results indicate that <italic>MYC</italic> amplification could occur in ring chromosomes without dmin. A cryptic <italic>MYC</italic> deletion suggests that an episome model could be applicable to <italic>MYC</italic> amplification in ring chromosomes as observed for dmin and hsr. Furthermore, considering 2 further reported cases, t(11;16)(q13;p11) may be a very rare but recurrent translocation in AML. [ABSTRACT FROM AUTHOR]