What is the cause of osteosarcoma?

The main tissue components of osteosarcoma are tumor osteoblasts, tumor osteoid tissue and tumor bone. The amount of its components varies with the degree of differentiation of tumor osteoblasts. Those with more advanced differentiation have more tumor bone, which is called sclerotic osteosarcoma, while those with more primitive differentiation have less tumor bone, which is called osteolytic osteosarcoma. Those in between the two are osteolytic and sclerotic osteosarcomas of varying degrees.

Under naked eye observation, the nature of osteosarcoma is quite inconsistent. Some are as hard as ivory (sclerotic osteosarcoma), some are as brittle and soft as granulation tissue that bleeds easily and has very little tumor bone (osteolytic osteosarcoma), some grow rapidly but lack blood, resulting in partial necrosis of the tumor and formation of cysts containing brown or bloody fluid; some grow rapidly and have rich blood supply, with tumor tissue containing a large number of dilated blood vessels and blood, resulting in pulsation and murmurs, forming a pseudoaneurysm.

Microscopic examination shows that the composition of tumor tissue is also complex and unpredictable. In the sections of the sclerotic part, it is possible to find tumor trabeculae that are not layered, have no canalicular system, are arranged in a disordered manner, and are stained quite deeply. There may be undamaged normal bone in the gaps between the tumor trabeculae. Compared with the tumor bone, it further shows the disorder of the tumor trabeculae that do not obey the principle of physiological force lines. In the sections of the lytic part, it can be found that the tumor bone is scarce or non-existent, and there may be scattered bone-like tissue occasionally, but there are a lot of tumor osteoblasts, which are primitively differentiated, of different sizes, with uneven cytoplasm, unclear cell membranes, large nuclei, dark staining, and many divisions. In addition, there are abundant blood vessels, some of which are sinusoidal, and their walls are formed by tumor cells. The different tissue images under the above two microscopes may exist in the same osteosarcoma. This shows that once osteosarcoma occurs, regardless of whether it is sclerotic or lytic, the degree of malignancy cannot be very different. In addition to the above microscopic findings, two relatively rare cells can be found: one is the tumor giant cell, which has as many as 3-10 nuclei and is deeply stained, and the other is the foreign body giant cell, which is scattered around the necrotic or hemorrhagic part of the tumor. Its morphology is the same as that of the giant cell of giant cell tumor of bone. In general, the main components of osteosarcoma are tumor osteoblasts, osteoid tissue and tumor bone. However, there may also be some small islands of cartilage tissue with varying degrees of malignancy, which are small in number and cannot affect the nature of osteosarcoma. The name of osteosarcoma should not be changed due to the appearance of cartilage tissue.

Early symptoms of osteosarcoma

Pain is an early symptom that can occur before the tumor appears. It is intermittent at first, and gradually turns into continuous severe pain, especially at night. Pain in large malignant osteosarcoma occurs earlier and is more severe, often with a history of local trauma.

The tumor near the bone end is large, with varying hardness, tenderness, high local temperature, dilated veins, sometimes palpable pulsation, and pathological fractures. Overall health gradually declines to failure, and most patients have lung metastasis within a year.

X-ray film manifestations: Bone density is different. There is irregular destruction, blurred surface, unclear boundaries, and lesions mostly start from the epiphyseal end. Due to tumor growth and periosteal reaction, Kauderman's triangle is formed, and there are radial bone needles perpendicular to the bone shaft.

Clinically, adolescents with pain and swelling near the knee joint should be carefully examined. Most cases can be diagnosed based on medical history, physical signs and X-ray findings, and a biopsy should be performed if necessary. Attention should be paid to distinguishing from the following lesions: myositis ossificans, tuberculous osteitis of the metacarpals and metatarsal bones (osteosarcoma rarely occurs here), chronic osteomyelitis, bone cysts and giant cell tumors.