Multiple Clonal TCR Gene Rearrangements Are Typical in Peripheral T-Cell Lymphoma Not Otherwise Specified

Introduction: Peripheral T-cell lymphoma not otherwise specified (PTCL-NOS) is a heterogeneous subgroup of PTCL with no consistent immunophenotypic, genetic and clinical features. PTCL-NOS represents less than 29% of all T-cell lymphomas in adults and often has an aggressive course with extranodal and systemic involvement. This study is focused on the application of clonality testing methods for PTCL-NOS diagnosis and monitoring.

Patients and Methods: Biopsies, blood and bone marrow samples were tested for 30 patients with PTCL-NOS: the ratio of male/female was 15/15, median age was 56 years (32-75), and 22 of 30 patients had IV stage of the disease. TCRG and TCRB gene rearrangements were evaluated for T cell clonality analysis. We used PCR-based methods (BIOMED-2 standardized clonality protocol) followed by GeneScan analysis on the ABI PRISM 3130 Genetic Analyzer (Applied Biosystems).

Results: Clonal TCR gene rearrangements were found in 29 of 30 patients (97%): TCRG in 27 of 30 (90%) and TCRB in 29 of 30 (97%). Primary biopsies or bone marrow samples showed oligoclonal pattern of rearrangements (more than 3 clonal peaks in TCRG or TCRB GeneScan profiles) in 13 of 30 patients (43%). New clonal rearrangements in affected tissues (skin, tonsil, CSF, lymph nodes and etc.) during disease progression were found in 15 of 24 (63%) patients. Various representations of clonal rearrangements in different tissues indicate the presence of several tumor clones in the majority of cases (19 of 30 patients; 63%). The presence of several clones correlated with the number of tissues examined (rs = 0.6, p <0.0005). The detection rate of additional clonal rearrangements was 90% (9 of 10 patients) when 3 and more tissues were tested. The number of clonal rearrangements was not correlated with age (p = 0.43) or the stage of disease (p = 0.29). One can speculate that the presence of multiple clones in the PTCL-NOS could reflect genetic instability of this tumor.

Conclusion: Oligoclonality, clonal evolution and the appearance of new clones in the progression of the disease are typical features of PTCL-NOS. Multiple clonal rearrangements complicate diagnostics and assessment of minimal residual disease in this disease.