CEA (carcinoembryonic antigen) is an epithelial marker expressed in a wide range of adenocarcinomas. Staining is cytoplasmic, sometimes with membrane enhancement. It can be used as part of a panel to separate pulmonary adenocarcinoma (pos) from mesothelioma (neg) in pleural effusions. Polyclonal CEA shows a canalicular staining pattern in hepatocellular carcinoma, unlike metastatic adenocarcinoma or biliary duct carcinoma which are often in the differential diagnosis. It has also been shown to distinguish cutaneous hidradenoma (pos) from cutaneous clear cell renal cell carcinoma (neg).