[Dedifferentiated chordoma of the skull base. A case report].

Sarcomatous transformation in chordoma is a very rare condition and has been emphasized as a distinct entity because of its more aggressive clinical course. Here we describe a case of dedifferentiated chordoma arising from the skull base region of an 11-year-old boy, with tumor recurrence within one year. This tumor showed features of pleomorphic cell sarcoma with areas more typical of chordoma. Most of tumor cells expressed cytokeratin, epithelial membrane antigen, vimentin and S-100 protein, thus confirming the diagnosis of dedifferentiated chordoma.