Characterization of TCR Expression in Paraffin Embedded Tissue Sections: A New Diagnostic Tool for T-Cell Lymphomas
A Garcia, N Villamor, P Gaulard, E Jaffe, E Campo, A Martinez. Hospital Clinic, Barcelona, Spain; Hospital Henri Mondor, Creteil, France; National Cancer Institute, Bethesda
Background: Human T lymphocytes constitute a small proportion (1-5%) of the peripheral blood (PB) lymphocytes, but represent up to 50% of T-cells in the skin and in the mucosa of the gastrointestinal (GI) tract. Malignant neoplasms derived from these cells are uncommon. The precursor T-cell lymphoblastic leukemia/lymphoma and hepatoesplenic T-cell lymphoma are the more frequent subtypes. T-cell lymphomas ( TCL) involving mucosal surfaces and skin also have been recognized. The use of chain specific monoclonal antibodies (MAbs) against TCR in pathology is hampered by their restricted application to frozen tissue. The purpose of this study was to validate the utility of MAb for human TCR constant region on paraffin-embedded samples.
Design: We performed immunohistochemical (IHC) staining for TCR expression in normal human tissues and a series of 33 T-cell lymphomas including 27 tumors suspicious of T-cell differentiation. Five cases diagnosed of peripheral T-cell lymphoma unspecified (PTCL) and 1 extranodal NK/T cell lymphoma were used as negative control. A 10% neutral buffered formalin was used in 26 cases and 7 were fixed in Bouin's solution (BS). We used a 5A6.39 MAb against -chain. -chain was also analyzed in all cases. A cell pellet of negative sorted PB T-cells was used as a control.
Results: A normal population of intraepithelial lymphocytes with expression of -chain was observed in the GI tract and the splenic red pulp. An optimal staining was obtained in 20 formalin fixed samples and the IHC failed in 13 cases including all samples fixed in BS. A -chain expression was observed in 12 out of 20 cases (60%) priory diagnosed of TCL. In two of them we corroborated the IHC results using flow cytometry. Two cases priory diagnosed of TCL were negative with a good internal control and also lack -chain expression. In addition, 5 PTCL and 1 extranodal NK/T cell lymphoma, nasal type were studied for -chain expression. All of them were negative for- chain and 4 showed -chain expression.
Conclusions: The detection of T cells in paraffin sections is possible and allow the recognition of tumors that although clinically, phenotypically and morphologically mimics a TCL lacks a T-cell differentiation. Nevertheless, the standardization of the IHC for -chain in the clinical settings is challenged by the preanalytical variability and requires a good fixation in 10% neutral formalin.
Wednesday, March 11, 2009 9:30 AM
Poster Session V # 193, Wednesday Morning