Sarcomatous transformation in cranial chordoma

In a study of 52 patients with cranial chordoma treated at the Mayo Clinic over a 19-year period (1966-1984), two tumors showed anaplastic features, both de novo, i.e., unassociated with prior irradiation. The incidence of anaplastic transformation was thus 4%. Immunohistochemistry showed the mixed mesenchymal-epithelial phenotype typical of chordoma in portions of both tumors, but loss of reactivity for keratin and epithelial membrane antigen was noted in anaplastic components. The study indicates that sarcomatous change in chordoma is a rare event that may occur de novo and is associated with the loss of immunophenotypic features of epithelial differentiation.