Pediatric osteosarcoma is a kind of bone cancer that predominantly occurs in adolescents and young adults between the ages of 10 and 25. The peak age is around 15, when the long bones are undergoing a major growth spurt. Cases of osteosarcoma are divided about equally between boys and girls until the age of 13, after which male cases start to predominate. There are approximately 400 new cases per year in the US.
Bone cancers account for approximately 5 to 6 percent of the tumors of childhood, and osteosarcoma represents 56 percent of these tumors. It is the fourth most common site of childhood cancer, behind leukemia, lymphoma and brain tumors. Another, closely related, bone tumor, Ewing's sarcoma, accounts for another 34 percent. Osteosarcoma is slightly more common in whites than in blacks whereas Ewing's sarcoma is almost six times more common in whites than in blacks.
There appears to be no single cause of osteosarcoma. However, there are certain fairly well identified associations and risk factors. For example, people who have a rare inherited disorder called the Li-Fraumeni syndrome have a higher than normal rate of developing cancers, including osteosarcoma. This points to a genetic component to this disease. Similarly, children who have had retinoblastoma (a rare tumor of the eye) have an increased risk of osteosarcoma as well. Both conditions are prone to have mutations of the RB1 gene.
It appears certain that rapid bone growth is also a key contributory factor to the development of this disease, since the most common sites of occurrence are typically in those areas of bone that are most rapidly dividing (the areas closest to the 'growth plates' or 'physes'). Over 90 percent of osteosarcomas are located in the growing ends of the long bones, and about 80 percent of them are to be found around the knee, either at the upper end of the tibia or at the lower end of the femur. It also occurs at the end of the upper arm bone (humerus) that is nearest the shoulder. A relatively small number of osteosarcomas occur in sites such as the rib, clavicle, pelvis or the flat bones of the skull and face. but these tumors are somewhat different from other osteosarcomas. Tumors of the craniofacial or other flat bones have good survival after a complete removal of the involved bone; however surgery for tumors in such sites can be difficult and disfiguring.
The symptoms of osteosarcoma tend to be pain, with or without swelling, in the long bones. The affected area may feel hot. Sometimes the osteosarcoma is first noticed when the child or teen has an incidental injury to the area. The injury does not cause the tumor (as was formerly thought) but merely brings it to everyone's attention. A persistent, unexplained limp in a child is a warning sign of a possible tumor. The range of motion of the joint may also be decreased.
Not all osteosarcomas develop as solitary lesions in the long bones. It is not uncommon for there to be multiple sites of malignancy, or for the disease to begin as a solitary lesion only for other sites to develop in parallel within a few months of the initial diagnosis. The chief symptom of the disease is pain, particularly pain on activity. If the disease has already spread to the lungs there may be respiratory symptoms such as breathlessness also.
