Identification of the Tumor Cells in Peripheral T-Cell Lymphomas by Combined Polymerase Chain Reaction-Based T-Cell Receptor β Spectrotyping and Immunohistological Detection with T-Cell Receptor β Chain Variable Region Segment-Specific Antibodies

Most nodal peripheral T-cell lymphomas (PTCL) originate from αβ-T cells, and they often contain reactive T cells that may hamper immunophenotyping. To specifically identify the neoplastic population in immunohistochemically stained slides, we assessed the heterogeneity of the T-cell receptor β chain variable region (TCRVβ). This region contains 65 gene segments, of which only one is expressed after rearrangement. To investigate PTCL, we developed a polymerase chain reaction assay to define the clonally rearranged TCRVβ segment. Detecting the corresponding epitope with segment-specific antibodies enabled identification of tumor cells among the T cells. The TCRVβ segment of the tumor cells was defined in 13 of 13 PTCL not otherwise specified and 11 of 13 angioimmunoblastic T-cell lymphomas. Antibodies corresponding to the respective TCRVβ segment of the tumor were available for seven cases from each group. After applying these antibodies in combination with antibodies against CD3, CD5, CD4, CD8, and cytotoxic molecules, double stains were evaluated by confocal laser scanning microscopy. In 9 of 14 cases, less than 50% of T cells expressed the clonally rearranged TCRVβ segment. Phenotypes defined in double stains differed from those obtained by conventional immunohistochemistry in 11 of 14 cases. The combination of TCRVβ polymerase chain reaction and immunohistochemistry may facilitate more reliable detection and characterization of tumor cells in PTCL.