cyTRBC1 evaluation rapidly identifies sCD3‐negative peripheral T‐cell lymphomas and reveals a novel type of sCD3‐negative T‐cell clone with uncertain significance

Abstract

AbstractThe flow cytometry‐based evaluation of TRBC1 expression has been demonstrated as a rapid and specific method for detecting T‐cell clones in sCD3‐positive TCRαβ+ mature T‐cell lymphoma. The aim of the study was to validate the utility of surface (s) TRBC1 and cytoplastic (cy) TRBC1 assessment in detecting clonality of sCD3‐negative peripheral T‐cell lymphomas (PTCLs), as well as exploring the existence and characteristics of sCD3‐negative clonal T‐cell populations with uncertain significance (T‐CUS). Evaluation of sTRBC1 and cyTRBC1 were assessed on 61 samples from 37 patients with sCD3‐negative PTCLs, including 26 angioimmunoblastic T‐cell lymphoma (AITL) patients and 11 non‐AITL patients. The sCD3‐negative T‐CUS were screened from 1602 patients without T‐cell malignancy and 100 healthy individuals. Additionally, the clonality of cells was further detected through T‐cell gene rearrangement analysis. We demonstrated the monotypic expression patterns of cyTRBC1 in all sCD3‐negative PTCLs. Utilizing the cyTRBC1 evaluation assay, we identified a novel and rare subtype of sCD3‐negative T‐CUS for the first time among 13 out of 1602 (0.8%) patients without T‐cell malignancy. The clonality of these cells was further confirmed through T‐cell gene rearrangement analysis. This subset exhibited characteristics such as sCD3‐cyCD3 + CD4 + CD45RO+, closely resembling AITL rather than non‐AITL. Further analysis revealed that sCD3‐negative T‐CUS exhibited a smaller clone size in the lymph node and mass specimens compared to AITL patients. However, the clone size of sCD3‐negative T‐CUS was significantly lower than that of non‐AITL patients in both specimen groups. In conclusion, we validated the diagnostic utility of cyTRBC1 in detecting sCD3‐negative T‐cell clonality, provided a comprehensive analysis of sCD3‐negative T‐CUS, and established a framework and provided valuable insights for distinguishing sCD3‐negative T‐CUS from sCD3‐negative PTCLs based on their phenotypic properties and clone size.