The size of osteosarcoma is generally difficult to measure. By undergoing radiographic examination, Codman's triangle and bone destruction can be observed in the patient's images, which can be diagnosed as osteosarcoma. Further biopsy is then required. Osteosarcoma typically presents as a mass approximately the size of a fist, and early stages may involve malignant pulmonary metastasis. By conducting a pulmonary CT scan, lesions and metastatic foci can be discovered, primarily indicating bone destruction and the presence of Codman's triangle. Such destruction can deform the normal bone structure, and abnormal masses may be palpable during physical examinations, presenting in irregular shapes. This condition is commonly seen and cannot be evaluated merely by the size of the osteosarcoma. Early stages may involve lung metastasis, progressing to advanced stages where the prognosis is poor and survival rates significantly decrease. Therefore, this disease generally requires early diagnosis and treatment.