Evaluation of a new paraffin-reactive CD7 T-cell deletion marker and a polymerase chain reaction-based T-cell receptor gene rearrangement assay: Implications for diagnosis of mycosis fungoides in community clinical practice

Background. T-cell deletion and T-cell receptor (TCR) gene rearrangement st udies are helpful in the early diagnosis and subsequent management of mycos is fungoides (MF). However, this often requires fresh frozen tissue that ca n be difficult to obtain and evaluate in community clinical practice. A new CD7 antibody, the most sensitive and specific T-cell deletion marker, and a new TCR-y gene rearrangement polymerase chain reaction (PCR) assay (TCR-g amma PCR) are now available on routine paraffin-embedded biopsy specimens. Objective: Our purpose was to assess the utility of CD7 deletion and TCR-ga mma PCR in the diagnosis of MF using routine paraffin-embedded biopsy mater ial. Methods: Cases of MF (n = 17) with matching frozen tissue immunohistochemis try and benign reactive dermatoses (lichen planus; n = 27) were assessed fo r CD7 (Clone: CD7-272) deletion and TCR-gamma PCR using paraffin-embedded b iopsy specimens. Results: Excellent concordance comparing frozen and paraffin embedded CD7 i mmunostaining (88%) was observed, CD7 deletion and TCR-gamma PCR was sensit ive (94%) and specific (96%) for a diagnosis of NIF using paraffin-embedded biopsy specimens. Conclusion: In the diagnosis of IMF, detection of CD7 deletion and monoclon al TCR rearrangements can be successfully performed in a cost-effective, ti mely fashion using routine formalin-fixed paraffin-embedded biopsy specimen s.