Chordoma.

Chordoma is said to occur at the extremes of life and the extremes of the axial skeleton. (60 percent in base of skull, 30 percent in sacrum. Its peak incidence is 35 years for the cranial ( clivus ) tumours and 50 years for the sacral tumour. The tumour may occur at any age and at any site in the axial skeleton. It is more common in men. Chordomas are derived from notochordal remnants, have a mucoid vacuolated appearance and grow slowly, being destructive and invasive of local structures.