Enhanced sensitivity with a novel TCRγ PCR assay for clonality studies in 569 formalin-fixed, paraffin-embedded (FFPE) cases2

Background : Clonal rearrangement of genes encoding the immunoglobulins (Ig) and T-cell antigen receptors (TCR) are considered to be useful markers for the diagnosis of lymphoma and for determining the clonal origins of B- and T-cell populations in lymphoid neoplasms. Methods and Results : Polymerase chain reaction-based clonality assays for TCR γ , TCRβ, and immunoglobulin (Ig) heavy chain (IgH) gene rearrangements were evaluated for diagnostic sensitivity and specificity in 569 formalin-fixed, paraffin-embedded (FFPE) tissues. Combined TCRβ and TCRγ assays enhanced the routine detection of TCR clonality to 90% of all peripheral T-cell lymphoma (PTCL) cases. IgH clonality was detected in 59% of 241 peripheral T-cell lymphoma (BCL) cases and 6% of 169 PTCL cases. Of 452 lymphomas, 5% could not be classified phenotypically as B or T lineage after immunohistochemical and clonality studies. Of all BCL cases analyzed, 24% had detectable TCRβ and/or TCR γ clonality. Of these BCL with biclonal results, 47% were extranodal lymphomas from skin and various tissues. Conclusions : Clonality assays were useful for distinguishing reactive or benign lymph nodes from neoplastic lymphoid infiltrates in most cases. The inclusion of TCRβ and TCR γ assays in the assessment of lymphomas results in a significant increase in the sensitivity of clonality detection, but is of limited utility in assessing the T- or B-cell phenotype of the tumor.