<prompt> A 50-year-old patient presents with a lesion in the midline involving the sacrum. It is found to be sclerotic. What is the most probable diagnosis -MetastaticChordomaOsteosarcomaChondrosarcoma  <response>: Sclerotic lesion involving midline in the sacrum is likely to be chordoma.It occurs most commonly at either end of notochordmidline in following locationsSacrococcygeal regionClivusSuprasellar region 