Immunohistochemical and ultrastructural study of skull base chordomas.

Eight chordomas were studied by using specific antibodies against cytokeratin, vimentin, desmin, type II collagen, S-100 protein, epithelial membrane antigen (EMA), carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP). One chondrosarcoma was included as a representative of chondroid tumors. All chordomas were positively stained for epithelial markers (cytokeratin and EMA), whereas the chondrosarcoma was not. All chordomas and the chondrosarcoma expressed vimentin, type II collagen and S-100 protein. Oncofetal antigens (CEA and AFP) and desmin were found in five (63%) chordomas, whereas these antigens were not found in the chondrosarcoma. Ultrastructurally the chordoma cells showed junctional complexes, microvillous projections and basal lamina-like structures alongside the tumor cells, whereas the tumor cells of the chondrosarcoma had neither junctions and microvillous projections, nor basement membrane. The present study demonstrates the utility of these tumor markers and ultrastructural features in the differential diagnosis of chordomas and tumors with similar histologic patterns such as chondrosarcomas.