<prompt> 15 year old boy presented with a mass in the distal femur. X-ray from the lesion showed features of Codmans triangle and Sunray appearance. The diagnosis is:OsteosarcomaEwings sarcomaOsteoclastomaChondroblastoma  <response>: Codmans triangle and Sunray appearance are characteristic radiological findings in osteosarcoma. When the tumour elevates the periosteum of bone, a gap occurs between periosteum and bone, where the gap is elevated, bone is formed, creating a triangular shape on radiographs. Ref: Apleys system of ohopaedics and fractures;8th185; Essential ohopedics by Maheshwari 3rd219, 222. 