Epithelial Membrane Antigen in Papillary Thyroid Carcinoma and Multinodular Goiter; a Marker of Discrimination

Background: Papillary thyroid cancer is the most common type of thyroid malignancies. For a more accurate diagnosis, immunohistochemistry has been used widely in recent years. Epithelial membrane antigen has been detected in several benign and malignant lesions, and its use as a marker of malignancy has been sought in some studies. Objectives: The current study aimed to determine the presence and level of expression of epithelial membrane antigen in papillary thyroid carcinoma and multinodular goiter. Methods: Eighty-five samples of papillary thyroid carcinoma and 40 cases of multinodular goiter were stained histochemically for epithelial membrane antigen. The intensity of staining was classified in a semi-quantitative manner (1+ to 4+). Demographic data of the index cases, history of metastasis, and lymph node involvement, if any, were collected as well. Results: All PTCs and 87.5% of MNGs were positive for EMA. EMA was expressed more strongly in PTCs than in MNGs (P < 0.00). EMA reactivity was directly associated with lymph node involvement, capsular invasion, and size of the tumor (P = 0.008, P < 0.001, and P < 0.001, respectively). The intensity level of 2 or higher had high specificity for differentiating PTC from MNG. Conclusions: Strong expression of EMA may be a good marker of malignancy in differentiating PTC from MNG. This marker may also be regarded as an index of invasive behavior of PTC.