What is osteosarcoma? What is the incidence? Osteosarcoma, also known as osteogenic sarcoma, is the most common malignant tumor originating from bone, with a high degree of malignancy, rapid progression and easy metastasis. It is highly malignant, rapidly progressive, and easily metastatic. It accounts for approximately 4.4/million new cases per year in children and adolescents aged 0-24 years, or about 5% of all malignancies in children and adolescents. Where do osteosarcomas most commonly occur? About half of all osteosarcomas occur around the knee joint, that is, the upper calf and lower thigh. The rest can occur in the upper extremity, upper femur, iliac bone, spine, etc. Very few occur in the soft tissues and internal organs. Overseas statistics have shown that more than 1/5 of patients are found to have distant metastases at the time of consultation, with lung metastases being the most common. Early detection of tumor and timely medical treatment can reduce the chance of metastasis and improve the outcome. What are the manifestations of osteosarcoma? Pain is an early symptom of osteosarcoma, which may occur before the appearance of tumor, initially as intermittent pain, gradually turning into continuous severe pain, especially more serious at night. Tumors with high malignancy have earlier and more intense pain, often with a history of local trauma, obvious swelling of soft tissues at the primary site, varying hardness, pressure pain, venous dilatation on the skin surface, high local temperature, and sometimes pulsating sensation can be felt, and pathological fracture may occur even spontaneously after trauma. The whole body health gradually declines to failure, and patients with lung metastasis may also have corresponding metastatic symptoms such as cough and chest pain. Therefore, the occurrence of pain and swelling in the extremities, regardless of the history of trauma, should not be taken lightly and should be seen promptly.