Chordoma. Antibodies to epithelial membrane antigen and carcinoembryonic antigen in differential diagnosis.

Seven chordomas, chondrosarcomas, and mucinous colorectal carcinomas, five liposarcomas, and five ependymomas were evaluated for the presence of epithelial membrane antigen (EMA) and carcinoembryonic antigen (CEA) by using an immunoperoxidase technique. All of the chordomas and mucinous carcinomas were cytoplasmic EMA positive, while the chondrosarcomas, liposarcomas, and ependymomas were negative. Among the tumors that were studied, only the mucinous carcinomas were positive for CEA. The EMA positivity of a chordoma reflects its epithelial nature and is a valuable aid in making the differential diagnosis between a chordoma and nonepithelial tumors, while the absence of CEA in a chordoma aids in making the distinction between a chordoma and a mucinous carcinoma.