We examined the expression of Ep-CAM using the monoclonal antibody Ber-EP4 in 36 cases of thyroid tumors, including 4 adenomas, 11 papillary carcinomas, 5 follicular carcinomas, 8 medullary carcinomas, 2 poorly differentiated carcinomas, and 6 anaplastic carcinomas. We assessed the positivity as a predominantly membranous staining of the cells, and was scored according to the estimated percentage tumor cells in the total tissue section (negative: 0-10 %; positive: ≥10 %).