<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>: Ans. is b i.e., Chordoma Sclerotic lesion involving midline in the sacrum is likely to be chordoma. o It occurs most commonly at either end of notochord midline in following locations a Sacrococcygeal region b Clivus c Suprasellar region 