The Musashi-2 (MSI2) gene, at chromosome band 17q22, is recurrently associated with regulating normal hematopoiesis and promoting leukemia progression [1, 2]. MSI2 is overexpressed in human myeloid leukemia cell lines and its knockdown leads to decreased proliferation and increased apoptosis [2]. High expression of MSI2 protein may predict an unfavorable outcome in acute myeloid leukemia (AML) and adult B-cell acute lymphoblastic leukemia [2–4]. MSI2 rearrangement was first reported in two patients who presented with chronic myelogenous leukemia, and cryptic balanced translocations involving chromosomes 7 and 17 were discovered during disease progression [5]. The translocation involved identical breakpoints in chromosome 17q22 within the MSI2 gene in both cases [5]. One of these translocations resulted in a MSI2–HOXA9 chimeric fusion gene [5]. MSI2 rearrangement has also been reported in patients with myeloid leukemia and a 3; 17 translocation leading to EVI1 gene overexpression [6]. Here, we present a case of de novo AML exhibiting an unbalanced 10; 17 translocation leading to a TTC40–MSI2 fusion gene. To our knowledge this is the first report of this specific translocation.

A previously healthy 66-year-old woman presented with fatigue, and was found to have abnormal blood counts: hemoglobin 11.1 g/dL, white blood cells 58 10 3/µ L with 80% blasts and platelets 87 10 3/µ L. Her peripheral smear showed marked leukocytosis with increased blast forms that were intermediate in size and had round nuclei, dispersed chromatin, indistinct nucleoli and scant cytoplasm with rare azurophilic granules. No Auer rods were identified. Red blood cells and platelets were unremarkable. The bone marrow was hypercellular (95% cellularity), with a predominance (90–95% of cellularity) of intermediatesized blasts, similar to those seen in the blood. Maturing myeloid and erythroid cells and megakaryocytes were rare. Immunophenotyping by flow cytometry identified