Novel t(5;9)(q33;q22) fuses ITK to SYK in unspecified peripheral T-cell lymphoma

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Abstract
Among peripheral T-cell lymphomas (PTCL), the heterogeneous category of unspecified PTCL represents the most common subtype. Nevertheless, recurrent chromosomal translocations are unknown in this aggressive type of lymphoma. Here we describe a novel t(5;9)(q33;q22) in unspecified PTCL. Molecular analyses delineated the breakpoints to ITK and SYK resulting in a previously undescribed expression of the Syk tyrosine kinase by Itk. ITK–SYK transcripts were detected in five of 30 (17%) unspecified PTCL, but not in cases of angioimmunoblastic T-cell lymphoma (n=9) and anaplastic lymphoma kinase-negative anaplastic large-cell lymphoma (n=7). In all five translocation-positive cases, the breakpoints were identical fusing the N-terminal pleckstrin homology domain and proline-rich region of ITK to the tyrosine kinase domain of SYK. Three of the five t(5;9)(q33;q22)+ unspecified PTCL shared a very similar histological pattern with predominant involvement of lymphoid follicles and the same CD3+CD5+CD4+bcl-6+CD10+ immunophenotype. These results demonstrate the presence of a recurrent t(5;9)(q33;q22) in a subset of unspecified PTCL, which may represent a novel distinct subgroup of PTCL.