Osteosarcoma has the highest incidence among primary malignant tumors. This tumor is highly malignant with an extremely poor prognosis, often leading to lung metastasis within months. The 3-5 year survival rate after amputation is only 5-20%. Approximately three-quarters of all osteosarcomas occur in the lower femur and upper tibia, while other sites such as the humerus, upper femur, fibula, spine, and ilium may also be affected. Most are osteolytic, though a few are osteogenic. The disease can occur at any age but is most common between 10-25 years, with a higher incidence in males. The tumor is usually located at the bone end, though it may occasionally arise in the diaphysis or epiphysis. Osteosarcoma contains varying proportions of cartilage, fibrous tissue, and osteogenic tissue. It can infiltrate and spread beneath the periosteum, into the cortical bone, and the medullary cavity. In the early stages, the main tumor mass lies beneath the periosteum, fusing with the cortex. Osteolytic tumor tissue contains little cartilage and rapidly destroys bone, with rich circulation. Necrotic bone areas may form capsules, and the tumor can spread to adjacent soft tissues, potentially leading to pathological fractures. A few tumors exhibit dense bone formation. Generally, osteosarcoma does not invade joints, though joint involvement may occur if the cortex is destroyed or after a pathological fracture. Due to tumor progression and periosteal reaction, periosteal elevation often forms a triangular structure known as Codman's triangle, along with sunburst-like radiating bone spicules perpendicular to the diaphysis. Microscopically, numerous tumor cells are visible, with varying cell and nuclear sizes and shapes, including small multinucleated giant cells, spindle cells, immature chondrocytes, and malignant osteoblasts with large, deeply stained nuclei. Nearly all metastases occur hematogenously to the lungs, with a few spreading to the brain, viscera, kidneys, or lymph nodes via the lymphatic system.

Pain is an early symptom and may occur before the appearance of a tumor. Initially, it is intermittent pain, gradually turning into persistent severe pain, especially at night. Highly malignant tumors cause pain earlier and more intensely, often with a history of local trauma. Tumors near the bone ends close to the joints are large, with varying hardness, tenderness, elevated local temperature, dilated veins, and sometimes palpable pulsations. Pathological fractures may occur. Overall health gradually declines to exhaustion, and most patients develop lung metastases within a year.

X-ray findings: Bone density varies. There is irregular destruction with a blurred surface and indistinct boundaries. Lesions often originate from the epiphysis. Due to tumor growth and periosteal reaction, Codman's triangle forms, along with radiating bone spicules perpendicular to the shaft.

Clinically, adolescents with pain and swelling near the knee joint should be thoroughly examined. Based on medical history, signs, and X-ray findings, most cases can be diagnosed, with a biopsy performed if necessary.

Differential diagnosis should include the following conditions: myositis ossificans, subcutaneous nodular osteitis of the metacarpals and metatarsals (where osteosarcoma rarely occurs), chronic osteomyelitis, bone cysts, and giant cell tumors.

bubble_chart Treatment Measures

After a clear diagnosis, amputation or joint disarticulation should be performed as early as possible. Combining chemotherapy and radiotherapy before and after surgery may improve efficacy, whereas using chemotherapy or radiotherapy alone has limited effect.