Codman's triangle is seen in -

Ans. is 'a' i.e., Osteosarcoma o Codmanrs triangle and sun ray appearance are typical of osteosarcoma.o However, you should keep in your mind following very important facts : -Sunray (sunburst) appearance and codman's triangle indicates periosteal reaction (periosteal new bone formation),Both these are typical of osteosarcoma but may also occur in other rapidly growing bone tumors (Ewing's sarcoma), and infection (osteomyelitis).Similarly, onion peel appearance indicates periosteal new bone-formation and is typical for Ewing's sarcoma. But this can also occur in oseosarcoma and osteomyelitis.The crux is that, aggresivelv growing tumors and infection stimulate the periosteum which then react by forming new bone, (therefore it is called periosteal reaction) which may take any of the above form.o Sun-ray (sunburst) appearance and Codman's triangle: -Typical features of osteosarcoma,May also be seen in Ewing's sarcoma. osteomyelitis,o Onion-peel appearanceTypical feature of Ewing's sarcoma.May also be seen in osteosarcoma, and osteomyelitis