The skeletal system serves as the framework for the body and also protects the internal organs.  Bones grow by a process called remodeling.  During remodeling bone cells called osteoclasts eat away or resorb bone tissue.  Osteoblasts, another type of bone cell, add new bone to the holes created by osteoclasts.

Osteosarcoma is a type of bone cancer that occurs when osteoblasts mutate into cancerous cells.  These cancerous cells continue to divide at an increasing rate, forming a tumor.  Tumors usually develop in the growth plate, or metaphysis, the wide section of the bone that grows during childhood.  

Osteosarcoma can develop in any bone of the body.  However, it is more likely to develop in the femur, tibia, and humerus.  The most common symptoms of osteosarcoma are pain and swelling at the tumor site.

Osteosarcoma usually affects patients between the ages of 10 and 20, during the adolescent growth spurt.  Males and African-Americans are more likely to develop osteosarcoma.  A history of radiation therapy or having certain genetic factors also increases risk.  Treatment usually involves chemotherapy and surgery.