**3. Epidemiology**

Cranium base chordomas are unusual malignancies with an incidence rate of less than 0.2% among all intracranial neoplasms [8]. Population-based studies also confirmed that the overall frequency of chordomas in a year to be 0.08 per 100,000 persons [8]. All age groups have the chance to be affected with this disease but most of the cases are diagnosed during adulthood and hardly affect children and adolescents. Approximately 0.15% of all intracranial neoplasms are detected as Chondrosarcomas and it is 6% of all cranium base tumors [8].
