Amplification of the RARA gene in acute myeloid leukemia: significant finding or coincidental observation?

Oncogene amplification resulting in aberrant expression, although common in solid tumors, is rare in acute myeloid leukemia (AML) and is mostly associated with amplification of MYC, RUNX1, and MLL genes. Retinoic acid receptor alpha (RARA) and other target sequences at 17p11.2 often represent the amplicons expressed in breast cancer, not in AML. We present a unique case of a 59-year-old female with a history of breast cancer, now presenting with pancytopenia and bilateral infiltration with effusion in nodules of the right upper lobe of the lung. She was diagnosed with AML-M5. Chromosome analysis demonstrated a hypodiploid clone with complex numerical/structural abnormalities including 5q deletion, monosomy 7, as well as structurally rearranged chromosome 11 and several marker chromosomes. Fluorescence in situ hybridization (FISH) analysis showed amplification of RARA, loss of 7q, monosomy 7, loss of DEK (6p23), and additional copies of NUP214 (9q34) and MLL (11q23). Additional FISH studies showed both ERBB2 and TOP2A genes, which were co-amplified on one of the marker chromosomes. The follow-up bone marrow did not yield any metaphases, but FISH was normal for all probes, including RARA. After a short remission, the patient relapsed and showed clonal evolution. Additional case reports are necessary to assess whether RARA amplification in hematologic malignancies serves as an independent prognostic factor.