Clonal T-cell receptor gamma-chain gene rearrangement by PCR-based genescan analysis in advanced cutaneous T-cell lymphoma: A critical evaluation

Detection of clonal T-cell receptor gamma (TCR gamma)-chain gene rearrangem ent is a promising approach to distinguish between cutaneous T-cell lymphom as (CTCLs) and reactive T-cell infiltrates. Despite the improved sensitivit y by using the polymerase chain reaction (PCR) rather than Southern blot an alysis, monoclonality could be demonstrated in only 53-90 per cent of CTCL biopsies in recent studies. In the present study, formalin-fixed, paraffin- embedded specimens of 21 selected patients with clear-cut advanced-stage CT CL were analysed using a semi-nested TCR gamma PCR with newly developed con sensus primer pairs. Detection of PCR products was done by GeneScan analysi s (GSA); this technique is advantageous due to its sensitivity and accuracy in the detection and size determination of PCR products and it is easier t o interpret than direct read-outs from TGGE or DGGE gels. In serial dilutio n experiments, TCR gamma-PCR-GSA allowed the detection of clonal, rearrange d T-cells with a high in vitro sensitivity against a polyclonal background (6 per cent). Despite the selection of clear-cut, advanced-stage CTCL cases , however, dominant clonal TCR gamma-chain gene rearrangement,vas found in only 16 of the 21 patients analysed, indicating an overall clinical sensiti vity of 76 per cent. Specificity was evaluated using biopsy specimens from 21 control patients suffering from long-standing psoriasis (n = 13) and ecz ema (n = 8). Surprisingly, GeneScan profiles showing apparently single domi nant peaks were detected in 14 per cent of these skin lesions, but these pr ofiles turned out to be pseudo-monoclonal by repeated determinations. In co nclusion, TCR gamma-PCR-GSA does not suffice reliably to exclude malignancy , due to its limited clinical sensitivity but,vith precautions taken to det ect pseudo-monoclonality and to secure specificity, TCR gamma-PCR-GSA is a valuable instrument in the diagnosis of CTCL. Copyright (C) 1999 John Whey & Sons, Ltd.