Codman triangle – a distinctive triangular form of periosteal reaction seen when an aggressive bone lesion grows faster than new periosteum can be ossified. Only the periosteum at the very margin of the lesion has time to ossify creating a triangular lip of new bone. The most common causes of a Codman triangle include osteosarcoma, Ewing sarcoma and osteomyelitis. This patient had osteosarcoma which was further characterised with MRI.
from our tumblr blog