<s>[INST] context: Chordoma: This is a locally malignant, sometimes actually malignant tumour supposedly originating from the remnants of notochord. Sacrum and cervical spine are common sites. It presents with a persistent pain and swelling, sometimes with a neurological deficit. Bone destruction is the only hallmark feature of this tumour. Treatment, wherever possible, is complete excision. If complete excision is not possible, radiotherapy is done. Chordoma 1 It is a destructive bone tumor believed to arise from ectopic remnants of notochord/notochord cell rest. 2 Its maximum incidenceis between 50-70 years. 3 It is locally malignant with strong tendency to recur after excision. n Predilection for sacral (50%) and cranial (40%) regions (the extreme ends of the axial skeleton). 4 In sacrum at S4and S5and in cranium basisphenoid (clivus and dorsal aspect of sella) 5 Above sacrum and below C2, chordomas are rare. 6 Radiologically appears as a oval or lobulated well-defined purely lytic mass in midline, which may contain calcification and a soft tissue component. 7 Recurrence rate is high but its metastasis occurs late. 8 Chordoma at the base of skull carries best prognosis [/INST] question: Expansile lytic lesion of sacrum with specks of calcification is suggestive of | options: A: Osteosarcoma B: Secondaries in bone C: Chordoma D: Fibrous histiocytoma | answer: C </s>