Value of immunocytochemistry in aspiration cytology of sacrococcygeal chordoma. A report of two cases.

Two cases of saccrococcygeal chordoma that were diagnosed on the basis of smear preparations are presented. Only one case showed typical physaliferous cells. In both cases the final diagnosis was greatly facilitated by applying peroxidase-antiperoxidase immunocytochemistry techniques to the cytologic specimens. Chordomas coexpress epithelial markers, such as intermediate filaments of the cytokeratin type, epithelial antigens (such as tissue polypeptide and epithelial membrane antigen), intermediate filaments of the vimentin type and S-100 protein. This antigenic spectrum may greatly facilitate the differential diagnosis of chordoma from filum terminale ependymoma, chondroma and chondrosarcoma, metastases of clear cell-type carcinomas and schwannomas, and neurofibromas, even when the only specimens available are from aspiration cytology.