[506] Impact of TRG@ Clonality Studies on the Diagnosis of T Cell Lesions

Doha M Itani, John A Zic, Cindy Vnencak-Jones. Vanderbilt University Medical Center, Nashville, TN

Background: The diagnosis of cutaneous T cell lesions can be histologically challenging thus adjunct studies including: immunohistochemistry, flow cytometry, and T cell receptor gamma gene (TRG@) rearrangement studies are required. TRG@ studies can also be performed on peripheral blood (PB) for staging or to monitor disease status. The aim of this study was to evaluate the impact of TRG@ studies on the clinical diagnosis of T cell lesion.
Design: Institutional review board approval was obtained and medical records of patients with cutaneous T cell lesions (skin and/or PB) referred for TRG@ studies during 2004-2005 were reviewed. Study variables included: pathologic diagnosis of initial skin biopsy and frequency of TRG@ rearrangements (performed in house or at reference labs), frequency of PB testing, initial clinical diagnosis and final established clinical diagnosis on follow up.
Results: 91 cases were retrieved. 64/91 (70%) cases had a definitive histo-pathologic diagnosis on the initial skin biopsy. 26/64 (41%) had TRG@ assays ordered with concurrent results observed in 22/26 (85%), discordant results in 2/26 (8%) and inconclusive results in 2/26 (8%). PB involvement was determined by TRG@ assays in 15/40 (37.5%) cases as compared to 1 diagnostic case by flow cytometry and 2 diagnostic cases by Sezary preparations. Flow cytometry detected an atypical population of cells in 2 cases but these did not meet criteria for Sezary syndrome. 27/91 (30%) cases had an inconclusive initial histo-pathologic diagnosis and TRG@ studies had been ordered in all cases. One case had insufficient material for TRG@ studies and 7/26 (27%) cases had discordant histologic and TRG@ findings including 4 early mycosis fungoides (MF); 2 dermatitis cases and 1 case initially reported as MF which was subsequently determined likely to be a natural killer cell lymphoma.
Conclusions: Histology is superior to TRG@ assays in the diagnosis of skin lesions but TRG@ assays are more sensitive in detecting clones for PB involvement as compared to Sezary preparations and flow-cytometry. TRG@ assays provide important diagnostic information and are most useful when the pathologic diagnosis is inconclusive with 64% of these cases relying on these results to aid in the diagnosis. Further, the evaluation of T cell lesions is complex and the most accurate clinical diagnosis can be achieved when TRG@ rearrangement studies, histomorphologic findings and clinical information are simultaneously considered.
Category: Dermatopathology

Tuesday, March 20, 2012 9:30 AM

Poster Session III # 102, Tuesday Morning

 

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