Feasibility of T-cell receptor gamma (TCRgamma) gene rearrangement on formalin-fixed, paraffin-embedded tissues by PCR assays.

Introduction: T- and B-lymphocytes are involved in recognition of foreign antigen by the specificity of their surface T-cell receptor and immunoglobulin, generated by gene rearrangement. Each T- and B-lymphocyte carries unique rearranged TCR or immunoglobulin gene, which has been applied to detect clonal from non-clonal T- and B-cell proliferation. Methods: Paraffin-embedded biopsy tissues of 85 T-, 24 B-cell non-Hodgkin's lymphomas (NHL) of various subtypes, and seven reactive lymphoid hyperplasia were retrieved from the archives for determining the feasibility of TCRy gene rearrangement analysis by PCR assays in our laboratory. DNA was extracted by Proteinase K digestion. The analyses were performed by five PCR assays, and analysed on polyacrylamide gel. Results: Clonal TCRy gene rearrangement was demonstrated in 69/85 (81.2%) of the cases. Selective rearrangement of specific Vy segment was observed, especially in peripheral T-cell lymphoma-unspecified and nasal NK/T-cell lymphoma. Clonal TCRy rearranged band was also demonstrated in 4/24 (16.7%) and 2/7 (28.6%) of B-NHL and reactive lymphoid tissues respectively. Conclusion: PCR assays were able to demonstrate clonal TCRy gene rearrangement in a high proportion of T-NHL. However, the PCR results should be interpreted carefully. A neoplasm should only be considered as T-cell type if it does not express any B-cell marker because TCRy is not lineage specific as shown by the presence of clonal TCRy gene rearrangement in B-NHL. Hence, the results for TCR gene rearrangement should always be interpreted in conjunction with histology and immunophenotyping.