Identification of the MYST3-CREBBP fusion gene in infants with acute myeloid leukemia and hemophagocytosis

BACKGROUND Acute myeloid leukemia presenting the MYST3-CREBBP fusion gene is a rare subgroup associated with hemophagocytosis in early infancy and monocytic differentiation. The aim of this study was to define the relevant molecular cytogenetic characteristics of a unique series of early infancy acute myeloid leukemia cases (≤24months old), based on the presence of hemophagocytosis by blast cells at diagnosis. METHODS A series of 266 infant cases of acute myeloid leukemia was the reference cohort for the present analysis. Acute myeloid leukemia cases with hemophagocytosis by blast cells were reviewed to investigate the presence of the MYST3-CREBBP fusion gene by fluorescence in situ hybridization (FISH) and reverse transcription polymerase chain reaction. RESULTS Eleven cases with hemophagocytosis were identified with hemophagocytic lymphohistiocytosis being ruled out. Six cases were classified as myelomonocytic leukemia, three as AML-M7 and two as AML-M2. In five cases, the presence of the MYST3-CREBBP fusion gene identified by molecular cytogenetics was confirmed by fluorescence in situ hybridization. All patients received treatment according to the Berlin-Frankfürt-Münster acute myeloid leukemia protocols and only one out of the five patients with the MYST3-CREBBP fusion gene is still alive. CONCLUSIONS Our findings demonstrate that the presence of hemophagocytosis in acute myeloid leukemia was not exclusively associated to the MYST3-CREBBP fusion gene. Improvements in molecular cytogenetics may help to elucidate more complex chromosomal rearrangements in infants with acute myeloid leukemia and hemophagocytosis.