Immunohistochemistry of ecchordosis physaliphora and chordoma
Immunohistochemical stains for cytokeratins, vimentin, epithelial membrane antigen, carcinoembryonic antigen and S-100 were performed on nine ecchordoses and 10 chordomas. 100% of the ecchordoses were positive for cytokeratin, vimentin and epithelial membrane antigen. 78% were S-100 positive. 100% of the chordomas stained positively for cytokeratin, vimentin and S-100 and 90% were positive for epithelial membrane antigen. No ecchordosis or chordoma was carcinoembryonic-antigen positive. These findings are interesting for two reasons. First, the similar staining properties of chordoma and ecchordosis physaliphora support the embryologic hypothesis of their common origin from the fetal notochord. Second, they indicate that when an ecchordosis causes symptoms prompting surgical resection, differentiation of the lesion from chordoma with routine immunohistochemistry would not be helpful.