Comparative investigations of T cell receptor gamma gene rearrangements in frozen and formalin-fixed paraffin wax-embedded tissues by capillary electrophoresis.

Aim: To compare clonal T cell receptor gamma (TCRgamma) gene rearrangements in frozen and formalin-fixed paraffin wax-embedded (FFPE) tissue, using capillary electrophoresis for use in diagnostics, as T cell lymphomas may be difficult to diagnose by conventional methods.

Methods: The DNA for PCR was extracted from frozen and FFPE tissue, cell lines and blood. PCR primers Vgamma1-8, Vgamma9, Vgamma10 or Vgamma11 (5' end labelled) combined with a mixture of JgammaP1/JgammaP/JgammaP2/Jgamma2 (unlabelled) were used. Monoclonal cases were sequenced and clonality, reproducibility, sensitivity and specificity analyses were carried out.

Results: In all cases the molecular test was found to be in agreement with the histological diagnosis. Discrepancies were found between frozen and FFPE tissue in 18 of 56 (32%) tests. The method was highly reproducible. The sensitivity was found to be 0.5% for cell lines and 1% for patient specimens and the specificity 100%. The junctional region between the Vgamma and Jgamma segments was specific for each patient.

Conclusions: Capillary electrophoresis of PCR products from frozen and FFPE tissue is suitable for detecting clonal TCRgamma gene rearrangements. It is important, however, to correlate the results with conventional morphological and immunohistochemical studies.