This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pharmacology
Expansile lytic lesion at skull base typically involving clivus with specks of calcification is suggestive of NOT RELATED-RADIO 
Select and explain. 
A. Osteosarcoma, B. Secondaries in bone, C. Secondaries in bone, D. Fibrous histiocytoma
C: Secondaries in bone
Answer: C: Secondaries in bone 
Explanation: It is a destructive bone tumour believed to arise from ectopic remnants of notochord/ notochord cell rest.Its maximum incidence between 50-70 years.It is locally malignant with strong tendency to recur after excision.Predilection for sacral (50%) and cranial (40%) regions (the extreme ends of the axial skeleton); In sacrum at s4 and s5 and in cranium basisphenoid (clivus and dorsal aspect of sella)Above sacrum and below c2, chordomas are rare.Radiologically appears as a oval or lobulated well-defined purely lytic mass in midline, which may contain calcification and a soft tissue component.Recurrence rate is high but it metastasis occurs late.Chordoma at the base of skull carry best prognosis