TCRgamma-chain gene rearrangement by GeneScan: incidence and significance of clonal heterogeneity in Sézary syndrome.

GeneScan (GS) analysis is a highly sensitive method for the early detection of cutaneous T-cell lymphoma (CTCL) and allows the identification of clonal heterogeneity, defined as the coexistence of two or more different T-cell clones in multiple samples from the same patient. We analyzed by GS the incidence and the significance of long-lived oligoclonal expansions in multiple skin and blood samples from 24 Sézary syndrome (SS) patients, and tried to correlate them with the clinical outcome. A skin clonal heterogeneity with additional reproducible TCRgamma-gene rearrangements (TCRgamma-GRs) was detected at diagnosis in 19/24 patients, 13 of whom had a constant prevalence of pathological TCRgamma-GRs in both skin and blood (dominant clonal pattern). During follow-up, an increase in oligoclones that were present at diagnosis or the appearance of new oligoclones was observed in 10 patients; all of them achieved a clinical response to treatment with extracorporeal photochemotherapy (ECP). The TCRgamma pattern (homogeneity or heterogeneity) in the skin at diagnosis showed a relevant prognostic value, and patients with an oligoclonal pattern had a significantly longer survival than those with a homogeneous pattern. In conclusion, multiple-sample approach GS analysis allows the identification of clonal heterogeneity and could also help in identifying SS patients with a potential higher response to therapy.