THE POLYMERASE CHAIN-REACTION IN THE DEMONSTRATION OF MONOCLONALITY IN T-CELL LYMPHOMAS

Aims-To evaluate polymerase chain reaction (PCR) amplification of T ce ll receptor (TCR) beta and gamma chain genes as a means of demonstrati ng monoclonality in T cell lymphomas using histological samples; to co mpare the performance of PCR with Southern blot analysis. Methods-TCR- beta, TCR-gamma and immunoglobulin heavy chain (IGH) genes were analys ed using PCR in 55 cases of T cell lymphoma (28 frozen tissue and 27 p araffin wax embedded samples), diagnosed using morphological and immun ohistochemical criteria. The 28 frozen samples were subjected to South ern blot analysis using TCR-beta, TCR-gamma and IGH gene probes. Twent y five B cell lymphomas and 21 nonneoplastic lymphoid tissue samples w ere used as controls. Results-Using TCR-beta PCR, monoclonality was de tected in 24 (44%) of 55 T cell lymphomas compared with 43 (78%) of 55 using TCR-gamma PCR and in 82% with both techniques. Five (9%) of 55 T cell lymphomas were IGH PCR positive. None of the non-neoplastic lym phoid control samples were PCR positive. All B cell lymphomas showed a polyclonal pattern with TCR-B PCR while a single B cell lymphoma was positive using TCR-gamma primers. With TCR-beta PCR, a monoclonal resu lt was seen in 12 (43%) of 28 frozen samples of T cell lymphoma, compa red with 23 (82%) of 28 using Southern blot analysis. With TCR-gamma P CR, 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-gamma PCR shou ld be the method of choice for analysis of clonality in paraffin wax e mbedded sections of lymphoproliferative lesions, as TCR-beta PCR has a high false negative rate. Southern blot analysis remains the most suc cessful technique when sufficient fresh tissue samples and resources a re available.