The main symptom of osteosarcoma is localized pain, primarily at the distal end of the femur, the proximal end of the tibia, and the proximal end of the humerus. This pain tends to worsen continuously, with nighttime pain often more severe than during the day, which is a significant characteristic of osteosarcoma. The second symptom is the presence of a local mass, which is often spindle-shaped and generally located near a joint. This mass often leads to limited joint mobility, and the skin over the mass typically has a high temperature. Sometimes, it may also be accompanied by visible swelling of superficial veins. The third symptom involves systemic cachexia, which includes unexplained weight loss, generalized weakness, and even an anemic condition. The fourth point pertains to osteolytic osteosarcoma, which often leads to bone destruction, reduced bone strength, and consequently, even minor external forces can cause fractures. These are called pathological fractures. Thus, the symptoms of osteosarcoma generally include these four points.