Chordoma involving the skin: an immunohistochemical study of 11 cases.

Immunohistochemical properties were studied in 16 lesions from 11 patients with chordoma involving the skin. There were nine men and two women ranging from 21 to 62 years old (mean, 42.6). The initial tumor was sacrococcygeal in 10 cases and nasopharyngeal in 1 case. Three lesions represented a direct extension from the primary tumor to the skin, and 13 lesions were examples of local recurrences in the skin. Immunohistochemically, all lesions showed positivity for keratin, whereas 14 lesions were positive for vimentin and 12 for protein S-100. Epithelial membrane antigen was positive in four instances and carcinoembryonic antigen was negative in all studies. No significant difference was observed between the immunoprofile of cases of direct extension and those of local recurrences. Overall, the remarkable triple positivity for keratin, vimentin, and protein S-100 was observed in 11 lesions from eight different cases (73%). This study confirmed the utility of immunohistochemistry in the differential diagnosis of chordoma from tumors with similar histologic characteristics encountered in the skin.