Chordoma. An immunohistochemical study of 20 cases.

Twenty chordomas from 20 patients, including 17 nonchondroid and three chondroid types, were studied with a variety of antibodies directed against cytokeratin (AE-1/3), epithelial membrane antigen, carcinoembryonic antigen, S100 protein, vimentin, alpha 1-antichymotrypsin, and lysozyme. All 17 nonchondroid chordomas stained for cytokeratin, and most (16) stained for epithelial membrane antigen. In contrast, two chondroid chordomas failed to stain for either cytokeratin or epithelial membrane antigen, while one of them did stain for both antigens. Sixteen of the 20 chordomas (80%) stained for S100 protein, including all three chondroid chordomas. Vimentin was found in six (30%), and alpha 1-antichymotrypsin in 16 chordomas (80%). Carcinoembryonic antigen and lysozyme were each found in two specimens (10%). While these findings basically agree with the immunohistochemical studies of other investigators, there are a few discrepancies. Most significant is the lack of epithelial markers in two of three chondroid chordomas located at the base of the skull. Possible reasons for the discrepancies are discussed.