Classical and chondroid chordoma. A light-microscopic, histochemical, ultrastructural and immunohistochemical analysis of the various cell types.

The aim of the present investigation was to characterize the various cell types of classical and chondroid chordomas. Eight cases of classical chordoma, 1 case of sacrococcygeal chordoma with chondroid areas and 2 cases of spheno-occipital chondroid chordoma were studied. Ultrastructurally and immunohistochemically (immunoreactivity for cytokeratins, epithelial membrane antigen [EMA], tissue polypeptide antigen [TPA] and human milk fat globule protein [HMFG]) the 3 cell types (physaliferous, epithelial-like, and spindle-shaped) recognized light-microscopically presented features of epithelial differentiation and rather formed a continuous spectrum than being distinct cell types. The chondroid areas of the chondroid chordomas had similar ultrastructural and immunohistochemical properties except for the lack of immunoreactivity for EMA and HMFG. The results of the critical electrolyte concentration technique according to Scott and Dorling indicated that there was no difference in the sulfated glycosaminoglycan content between classical and chondroid chordomas: all the tumors contained chondroitin sulfate. The presence of chondroitin sulfate, immunoreactivity for vimentin and S-100 protein and areas of cartilaginous differentiation in three cases indicate a relationship both to chondromatous tumors and to normal notochord, from which chordoma is believed to originate.