OBJECTIVETo study the expression of EpCAM and E-cadherin in papillary thyroid carcinoma and to analyze its correlation with various clinicopathologic parameters.

METHODSImmunohistochemical study for EpCAM and E-cadherin was carried out in 91 cases of papillary thyroid carcinoma. Twenty-four cases of papillary hyperplasia of thyroid were used as controls.

RESULTSIn all of the 24 cases of papillary hyperplasia, EpCAM was located on the cell membrane, while in the 91 cases of papillary thyroid carcinoma studied, EpCAM was located within the cytoplasm, with 36.3% (33/91) showing nuclear localization as well. In all the papillary hyperplasia cases studied, E-cadherin showed membranous expression. E-cadherin expression was reduced in 84.6% (77/91) of papillary thyroid carcinoma, as compared with the surrounding native thyroid parenchyma. Amongst the 33 cases of papillary thyroid carcinoma which showed nuclear localization of EpCAM, 30 cases also showed reduced E-cadherin expression. There was a positive correlation between nuclear expression of EpCAM and loss of E-cadherin expression (P = 0.000; Spearman correlation coefficient = 0.857). Nuclear expression of EpCAM correlated with follicular variant of papillary thyroid carcinoma and presence of extrathyroidal extension ( P = 0.037 and 0.033, respectively). Loss of E-cadherin expression correlated with age of patients and presence of lymph node metastasis (P = 0.018 and 0.010, respectively).

CONCLUSIONSE-cadherin expression is reduced in papillary thyroid carcinoma, as compared with native thyroid parenchyma and papillary hyperplasia. Papillary thyroid carcinoma shows loss of EpCAM membranous expression and increased cytoplasmic/nuclear accumulation. Detection of these two markers may provide a valuable reference in defining the biologic behaviors of papillary thyroid carcinoma, including extrathyroidal extension and lymph node metastasis.