Trefoil factor 3 immunohistochemical characterization of follicular thyroid lesions from tissue microarray.

OBJECTIVES To characterize trefoil factor 3 (TFF3) expression in normal thyroid tissue samples compared with that in follicular adenoma, follicular carcinoma, and follicular variant of papillary thyroid carcinoma using immunohistochemistry on tissue microarrays. DESIGN Immunohistochemical analysis of 83 normal thyroid tissue and of 83 follicular neoplasms (26 follicular adenomas, 25 follicular variant of papillary thyroid carcinoma, 23 follicular thyroid carcinomas, and 9 papillary thyroid carcinomas) was performed using an antibody to TFF3 on tissue microarray sections composed of formalin-fixed, paraffin-embedded tissue samples. SETTING Academic research. PATIENTS Thyroid tissue samples collected from patients over a 15-year period were obtained from the University of North Carolina Hospitals Division of Surgical Pathology archives. MAIN OUTCOME MEASURES Thyroid tissue samples were graded by a pathologist based on intensity of antibody staining and on percentage of cells stained. Localization of TFF3 antibody was noted. Data were analyzed for semiquantitative differences in immunohistochemical intensity of antibody staining and in percentage of cells stained among normal thyroid tissue samples, follicular adenoma, follicular thyroid carcinoma, follicular variant of papillary thyroid carcinoma, and papillary thyroid carcinoma. RESULTS Semiquantitative analysis demonstrated that immunohistochemistry detects significant levels of TFF3 expression in normal thyroid tissue samples compared with that in follicular lesions based on intensity of antibody staining (P < .05). Only follicular thyroid carcinoma demonstrated a significant reduction in percentage of cells stained compared with that in normal thyroid tissue samples (P = .03). No significant differences in intensity of antibody staining or in the percentage of cells stained were noted among follicular adenoma, follicular thyroid carcinoma, follicular variant of papillary thyroid carcinoma, or papillary thyroid carcinoma. Trefoil factor 3 staining localized to the cytoplasm. CONCLUSIONS Protein expression data validate gene expression findings that follicular neoplastic lesions have decreased expression of TFF3 compared with that in normal thyroid tissue samples. These findings contribute to evidence suggesting that TFF3 may have a role in normal thyroid tissue function and that thyroid carcinomas may have reduced expression of TFF3, in contradistinction to other carcinomas that overexpress TFF3.