Osteosarcoma in children & teenagers — bone cancer child explained

Osteosarcoma is a type of cancer that starts in the bone-forming cells — called osteoblasts — which are responsible for building new bone. Instead of producing normal bone, these abnormal cells grow uncontrollably and form a tumour, usually inside the bone itself. Osteosarcoma is the most common primary bone cancer in children and teenagers, and it most often arises during the years of rapid bone growth — which is why it is most frequently seen in adolescents around the time of their growth spurt. The exact cause is not fully understood, but the cancer is not contagious, is not caused by anything the child or family did, and in most cases does not run in families. A small number of cases are linked to known genetic conditions, but the majority arise without any identifiable hereditary risk.

Osteosarcoma most often develops in the long bones of the body — the bones that are growing fastest during adolescence. The most common sites are the lower end of the femur (thigh bone, just above the knee), the upper end of the tibia (shin bone, just below the knee), and the upper end of the humerus (upper arm bone, just below the shoulder). The knee region accounts for the majority of cases in children and teenagers. Osteosarcoma can also develop in the jaw, skull, and pelvis, though these sites are less common. In younger children, the pelvis and axial skeleton (spine, ribcage) are more frequently involved than in teenagers. The location of the tumour affects how surgery is planned and which type of reconstruction is most suitable.

The most common first sign of osteosarcoma is persistent pain in a bone or joint — often described as a deep ache or throbbing — that does not go away with rest and may be worse at night. This pain is frequently mistaken for growing pains or a sports injury, which can delay diagnosis. A swelling or lump near a joint — most often the knee or shoulder — is another important warning sign. Unlike a soft-tissue bruise, this swelling arises from the bone itself and is usually firm. The child may begin limping or have difficulty using the affected limb. Reduced range of movement in the nearest joint is also common. Bone fractures from what seems like a minor injury (called a pathological fracture) can sometimes be how osteosarcoma is first noticed. Fever, weight loss, and extreme fatigue are less typical early features of osteosarcoma than they are of other childhood cancers, but they can be present in advanced disease.

Diagnosing osteosarcoma requires several steps. When a doctor suspects bone cancer, the first investigations are imaging studies — usually X-rays of the painful bone, which may show an abnormal area within the bone called a sunburst pattern or Codman triangle (changes in the cortex of the bone that are characteristic but not specific to osteosarcoma). An MRI of the affected bone gives a detailed view of the tumour's extent within the bone and in the surrounding soft tissue. A CT scan of the chest is performed to check whether the cancer has spread to the lungs, which are the most common site of spread. A biopsy is essential — a small piece of tumour tissue is removed and examined under a microscope by a specialist pathologist to confirm the diagnosis. The biopsy must be planned carefully by the surgical team, because a poorly planned biopsy can limit surgical options later. A bone scan or PET-CT may be used to check for spread to other bones.

The treatment of osteosarcoma in children almost always involves a combination of chemotherapy and surgery. Chemotherapy is typically given before surgery (called neoadjuvant chemotherapy) to shrink the tumour and destroy any cancer cells that may have already spread. After chemotherapy, the surgical team removes the tumour. In most children today, limb-salvage surgery is possible — this means the bone and joint are reconstructed rather than amputated, so the child keeps the limb. Reconstruction may use a metal implant (endoprosthesis), a bone graft, or a combination. The choice depends on the tumour's location, the child's age, and local expertise. After surgery, further chemotherapy is given (adjuvant chemotherapy) to reduce the risk of relapse. Radiation therapy is not routinely used for osteosarcoma, as the tumour is not highly sensitive to radiation; however, it may have a role in specific situations. The entire treatment plan is reviewed by a multidisciplinary team.

Yes — osteosarcoma can spread (metastasise) to other parts of the body. The lungs are by far the most common site of spread; this is why a CT scan of the chest is always part of the initial staging. Less commonly, osteosarcoma can spread to other bones. Whether the cancer has spread at the time of diagnosis is one of the most important factors in how the treatment is planned. Children whose osteosarcoma is confined to the primary bone site (localised disease) have a better overall outlook than those whose cancer has already spread at diagnosis (metastatic disease). This is one reason why early evaluation by a specialist team matters — the sooner an accurate diagnosis is made and staging is completed, the sooner a full treatment plan can be put in place. The CION team completes staging workup promptly so that treatment begins without delay.