Background: Chordoma is a rare, slowly growing tumor arising from notochordal rests and occurring in several anatomical locations with different clinical patterns of presentation. Dedifferentiation or sarcomatous transformation in a chordoma is a known but rarely recorded event.
Case: We report the case of a 58-year-old man diagnosed with chordoma of the clivus who, over the course of 5 years, showed histological and immunohistochemical evidence of progressive dedifferentiation in the tumor.
Conclusion: Sarcomatous transformation in chordomas is seen less frequently in the clival region. A high degree of suspicion and extensive sampling are essential for diagnosis, especially in recurrent tumors.