Epithelial cell adhesion molecule (EpCAM) is expressed by a broad variety of carcinoma cells. It is recognized by the monoclonal antibody 17-1A, which has already been applied for immunotherapy of several carcinoma types in preclinical and small clinical studies. In the present study the immunohistochemical properties of 17-1A were evaluated in 121 cases of thyroid carcinomas of follicular cell origin, comprising of 75 differentiated (DTC; 35 papillary and 40 follicular carcinomas), 24 poorly differentiated (PDTC) and 22 anaplastic thyroid carcinomas. Overexpression of EpCAM, as recently defined, was found with a distinct membranous staining pattern in 81.3% of DTCs and in 66.6% of PDTCs. In contrast, all anaplastic thyroid carcinomas (0%) completely lacked EpCAM expression. Normal thyroid tissue presented with weak and heterogeneous EpCAM staining. This study demonstrates EpCAM overexpression as a common finding in DTCs and PDTCs, and thus these tumors as possible novel targets for EpCAM-directed immunotherapy. Our findings suggest that patients with recurrent or advanced tumor disease and metastatic spread could benefit from this modern therapeutic regime, especially after insufficient radioiodine therapy.