VALUE OF PCR DETECTION OF TCR-GAMMA GENE REARRANGEMENT IN THE DIAGNOSIS OF CUTANEOUS LYMPHOCYTIC INFILTRATES

In this study, we analyzed the reliability and usefulness of the polym erase chain reaction (PCR) for the detection of T-cell receptor (TCR)g amma gene monoclonal rearrangement. We first tested for the specificit y and sensitivity of this strategy, against the classical criteria of Southern blot analysis (SBA). Of the 27 samples tested, results agreed in all but two. Broader analysis of these cases demonstrated the high specificity (absence of false positives) of the PCR strategy, togethe r with its limited sensitivity (10% of false negatives). The usefulnes s of this PCR approach was then tested on a panel of 28 biopsy specime ns of cutaneous lymphocytic infiltrates. Monoclonal TCR gamma rearrang ement was detected in seven of eight cases of early stage mycosis fung oides (MF), one of two Sezary syndrome (SS) cases, two of two non-MF T -cell lymphoma, and two of three lymphomatoid papulosis. Monoclonality was not detected in any of the 11 benign cases (parapsoriasis and inf lammatory dermatosis). Results-obtained with this new molecular strate gy provide additional support for the hypothesis of a monoclonal origi n for most early stage T-cell MF. They also suggest the heterogeneous nature of some lymphomatoid papulosis lesions. Therefore, due to the d ifficulty in detecting T-cell monoclonality by immunohistochemical tec hniques, PCR can be a useful alternative strategy to SBA. It could als o be used as a complementary technique in the routine diagnosis of T-c ell cutaneous infiltrates.