What is known as Codman's triangle on x-ray?

Codman's triangle is a radiological finding characterized by the elevation of the periosteum due to underlying bone lesions. This triangular area of new bone formation occurs as a result of aggressive bone tumors that lead to subperiosteal bone formation. In particular, osteosarcoma is one of the most common primary malignant bone tumors in adolescents that is associated with Codman’s triangle. This is because the aggressive nature of osteosarcoma causes a lifting of the periosteum, resulting in the characteristic triangular appearance on x-ray.

Ewing's sarcoma, another primary bone malignancy, can also present with similar features due to periosteal reaction and aggressive bone destruction. Although there are some differences between the two tumors in terms of age distribution and specific x-ray findings, both can produce a Codman’s triangle.

Therefore, the correct understanding of Codman's triangle encompasses both osteosarcoma and Ewing's sarcoma, as both can cause this specific radiological sign through their aggressive growth patterns and interactions with the periosteum. This distinguishes the correct answer as encompassing both osteosarcoma and Ewing's sarcoma as being known for this x-ray finding.