Molecular Cytogenetic Characterization of a Case of a Myelodysplastic/Myeloproliferative Neoplasm, Chronic Myelomonocytic Leukemia-1 (CMML-1) with Abnormal Karyotype with an Apparent Monosomy 7 Resulting in Rearrangements Involving Chromosomes 7 and 21.

Objectives: We report the case of a 69-year-old male with peripheral blood findings of persistent anemia, mild absolute monocytosis with mild dysgranulopoiesis, rare circulating blasts, and mild thrombocytopenia. Bone marrow biopsy revealed hypercellular bone marrow (60%) with 3.4% blasts and mild dysgranulopoiesis, morphologically characteristic of myelodysplastic/myeloproliferative neoplasm, chronic myelomonocytic leukemia-1 (CMML-1). Chromosome analysis revealed an abnormal karyotype with an apparent monosomy 7 and the presence of one marker chromosome. FISH analysis of metaphases from destained G-banded slides revealed translocation of D7S486 to a derivative chromosome 21, and two copies of RUNX1 located on an isoderivative chromosome 7. This karyotype was then reinterpreted as an abnormal male karyotype with rearrangements of chromosomes 7 and 21 [ider(7)(q10)t(7;21)(q11.2;q11.2), der(21)t(7;21)], resulting in loss of 7p and gain of 21q, in 19 of the 20 metaphase cells examined. The remaining one metaphase was cytogenetically normal. Extra copies of RUNX1 and abnormalities of chromosome 7 are seen in myeloid disorders including MDS/MPN. Complex rearrangements such as the ones present in this study suggest genomic instability, which is usually associated with a poor prognosis.