The polymerase chain reaction in the demonstration of monoclonality in T cell lymphomas

Abstract

Aims-To evaluate polymerase chain reaction (PCR) amplification of T cell receptor (TCR) β and γ chain genes as a means of demonstrating monoclonality in T cell lymphomas using histological samples; to compare the performance of PCR with Southern blot analysis. Methods-TCR-β TCR-γ and inmnunoglobulin heavy chain (IGH) genes were analysed using PCR in 55 cases of T cell lymphoma (28 frozen tissue and 27 paraffin wax embedded samples), diagnosed using morphological and immunohistochemical criteria. The 28 frozen samples were subjected to Southern blot analysis using TCR-β TCR-γ and IGH gene probes. Twenty five B cell lymphomas and 21 nonneoplastic lymphoid tissue samples were used as controls. Results-Using TCR-β PCR, monoclonality was detected in 24 (44%) of 55 T cell lymphomas compared with 43 (78%) of 55 using TCR-γ PCR and in 82% with both techniques. Five (9%) of 55 T cell lymphomas were IGH PCR positive. None of the non-neoplastic lymphoid control samples were PCR positive. All B cell lymphomas showed a polyclonal pattern with TCR-β PCR while a single B cell lymphoma was positive using TCR-γ primers. With TCR-β PCR, a monoclonal result was seen in 12 (43%) of 28 frozen samples of T cell lymphoma, compared with 23 (82%) of 28 using Southern blot analysis. With TCR-γ PCR, 19 (68%) of 28 frozen tissue samples were positive, compared with 26 (93%) of 28 using Southern blot analysis. A single case showed IGH rearrangement by Southern blot analysis. Conclusion-TCR-γ PCR should be the method of choice for analysis of clonality in paraffin wax embedded sections of lymphoproliferative lesions, as TCR-β PCR has a high false negative rate. Southern blot analysis remains the most successful technique when sufficient fresh tissue samples and resources are available.