Background: The Ep-CAM gene encodes a cancer-associated antigen that belongs to a family that includes at least two type I membrane proteins. It recognizes epithelial-associated glycoproteins located on the surface of the cell membrane and in the cytoplasm of almost all epithelial cells. It is not present in most squamous epithelial cells, hepatocytes, renal proximal tubular cells, gastric parietal cells, and myoepithelial cells. Studies have shown that Ep-CAM is expressed in the vast majority of adenocarcinomas and neuroendocrine tumors, including small cell carcinomas. Most malignant mesotheliomas are negative, so it can be used in the differential diagnosis of adenocarcinoma and mesothelioma.