Other Chromosomal Abnormalities

t(5;12)(q33;p13) occurs in 2-3% of CMML cases. The translocation results in a fusion oncogene TEL/ PDGFfiR. TEL is a transcription factor gene located on chromosome 12p13.1. It is involved in angiogenesis and hematopoesis. TEL fuses to the transmembrane and cytoplasmic domains of PDGFR, replacing the lig-and-binding site, and leads to autoactivation of the PDGFR.39'40 CMML patients with this translocation may benefit from therapy with imatinib mesylate as well as other tyrosine kinase inhibitors.40-42 Other translocations reported in CMML includes: t(5;17) (q33;p13) (Rabaptin-5/PDGFfiR),43 t(5;7)(q33; p11.2) (HIP1/PDGFM),44 and t(5;10)(q33;q21) (H4-D10S170/ PDGFfiR).43 Cytogenetic abnormalities are seen in 20-30% of CMML cases.45

t(3,21) is described in t-MDS/AML. EAP (Epstein-Barr virus small RNAs associated protein) at 3q26 fuses to the RUNX1 gene (AML gene) on 21q22 leading to truncation of RUNX1 and loss of its function. Two other genes described on 3q26 include EVI1 (ecotropic virus infection site) and MDS/EVI1 (MDS associated sequences). The MDS/EVI1 gene fuses to RUNX1, leading to a different EVI1 protein.31 Patients with MDS who have EVII abnormalities may benefit from therapy with arsenic trioxide.

The Philadelphia chromosome t(9,22) has been described in MDS. Ph+MDS patients had a median survival of 13 months in one review.46 Translocations seen in AML, such as t(8,21) or inv(16), have also been described in MDS.

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