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Aim: To assess the feasibility and informative value of T-cell clonality testing in peripheral T-cell lymphoma (PTCL). Patients and methods: Biopsies of involved sites, blood, and bone marrow samples from 30 PTCL patients are included in the study. Rearranged TCRG and TCRB gene fragments were PCR-amplified according to the BIOMED-2 protocol and analyzed by capillary electrophoresis on ABI PRISM 3130 (Applied Biosystems). Results: TCRG and TCRB gene clonality assay was valuable in confirming diagnosis in 97% of PTCL patients. T-cell clonality assay performed on blood or bone marrow samples reaffirmed lymphoma in 93% of cases, whereas morphological methods were informative in 73% of cases only. We observed multiple TCRG and TCRB gene rearrangements, loss of certain clones in the course of the disease, as well as acquisition of new clones in 63% of PTCL cases, which can be attributed to the genetic instability of the tumor. Conclusion: TCRG and TCRB gene clonality assay is beneficial for the diagnosis of PTCL. However, the presence of multiple clonal rearrangements should be considered. Clonal evolution in PTCL, particularly acquisition of new clones, should not be treated as a second tumor. Multiple TCRG and TCRB gene rearrangements may interfere with minimal residual disease monitoring in PTCL.

Clonal instability of a tumor cell population in acute lymphoblastic leukemia (ALL) may complicate the monitoring of a minimal residual disease (MRD) by means of patient-specific targets identified at the disease onset. Most of the data concerning the possible instability of rearranged clonal TCR and IG genes during disease recurrence were obtained for ALL in children. The appropriate features of adult ALL, which are known to differ from those of childhood ALL in certain biological characteristics and prognosis, remain insufficiently studied. The aim of this study was to assess the stability of IG and TCR gene rearrangements in adult ALL. Rearrangements were identified according to the BIOMED-2 protocol (PCR followed by fragment analysis). Mismatch in clonal rearrangements at onset and relapse was identified in 83% of patients, indicating clonal instability during treatment. Clonal evolution and diversity of IG and TCR gene rearrangements may be one of the tumor progression mechanisms. New rearrangements may emerge due to residual VDJ-recombinase activity in tumor cells. Also, many clonal IG and TCR gene rearrangements may be present at different levels at a diagnosis, but less abundant clones may be “invisible” due to limited detection sensitivity. Later, major clones may disappear in the course of chemotherapy, while others may proliferate. Investigation of clonal evolution and heterogeneity in ALL and their impact on the treatment efficacy will contribute to the identification of new prognostic factors and the development of therapeutic approaches.