[1332] A New Immunohistochemistry Method To Detect T-Cell Receptor gamma Chain Expression in Paraffin Embedded Biopsies Identifies a Unique Set of Peripheral T-Cell Lymphomas Co-Expressing T-Cell Receptor Beta and gamma Chains.

Nazan Ozsan, Andrew F Feldman, Bolette L Caron, Julie A Vrana, William G Morice, William R Macon, Paul J Kurtin, Ahmet Dogan, Karen L Grogg. Mayo Clinic, Rochester, MN

Background: Classification of peripheral T-cell lymphomas (PTCL) requires detailed immunophenotyping. The most important markers used in this context are cell surface molecules, and include T-cell receptor (TCR) α/β and γ/δ dimers. Although both TCR α/β and γ/δ expression can be determined by flow cytometry, and TCR β expression by paraffin immunohistochemistry (IHC), until recently no tests to detect TCR γ/δ on paraffin sections were available. In this study we describe a new IHC method that can detect TCR γ chain expression on paraffin sections of normal and neoplastic tissues.
Design: The study analyzed 275 cases including normal tissues and inflammatory lesions (N=50), non-lymphoid neoplasms (24), B-cell lymphomas (n=37), Hodgkin lymphomas (n=3), and PTCL (n=161) IHC was performed on paraffin sections using a monoclonal antibody against TCR γ chain (clone g3.20) and heat-mediated epitope retrieval. For PTCL cases, detailed diagnostic, immunophenotypic and genetic information was retrieved from the pathology reports.
Results: In normal tissues, most of the inflammatory lesions, non-lymphoid neoplasms and B-cell lymphomas TCR γ was expressed only by rare lymphocytes. Polyclonal TCR γ/δ lymphocytosis was rarely seen in spleen specimens and the intestinal biopsies performed for malabsorption (n=5). 21/161 of the PTCL expressed TCR γ. These included cases of PTCL, NOS (n=5), cutaneous γ/δ TCL (n=6), ALCL (n=2), EBV+ T/NK cell neoplasms (n=2), heaptosplenic T-cell lymphoma (N=4), and T-large granular lymphocyte leukemia (n=2). IHC also identified a subset of PTCL with co-expression of TCR β and γ chain (n= 3). These cases presented with cutaneous disease, high grade cytology and cytotoxic phenotype analysis, and molecular analysis showed rearrangement of both TCR β and γ chains. Where flow cytometric data on TCR γ/δ expression was available, there was 100% concordance with IHC.
Conclusions: 1. TCR γ expression can be detected by IHC on paraffin sections of normal and neoplastic tissues. 2. The frequency of PTCL expressing TCR γ may be more than initally recognized. 3. A subset of PTCL co-express TCR β and γ chains. These cases may represent a unique clinicopathological entity.
Category: Hematopathology

Tuesday, March 1, 2011 9:30 AM

Poster Session III # 226, Tuesday Morning

 

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