Introduction

Bone tumour rarely occurs in children. The two common types of bone tumours are Ewing's Sarcoma and Osteosarcoma.

I. Ewing's Sarcoma

Ewing's sarcoma is a kind of bone tumour, rare amongst the Chinese race. The tumour is also rare in children younger than 5 years of age.

Natural Development of the Disease

Most cases of Ewing's sarcoma arise from the bone, but in rare cases it may also arise from tissues other than the bone. The most common sites of involvement are the femur, the pelvic bone, the fibula, the tibia and the humerus.

It is common for the tumour to have spread to the lung on diagnosis. The other sites of spread include the bones and bone marrow.

Symptoms

The most common symptoms are pain and swelling of the affected bone. The swelling may be reddened and warm, mimicking osteomyelitis. It may rapidly enlarge. There may also be weakness and numbness of the affected limb because of nerve involvement by the tumour. In severe cases, the bone weakened by the tumour may fracture.

The initial symptoms also depend on the primary site of involvement. A patient may suffer from pleural effusion if a rib is involved, numbness of the chin and lip if the mandible is involved, or weakness and numbness of lower limbs if the spine is involved.

Other symptoms include fatigue, weight loss and fever, especially if there is already tumour dissemination.

Diagnostic Tests

The diagnostic procedures may include the following:

• Basic blood tests: to assess the vital functions of the body.
• X-ray and computerised tomography (CT) scan of the affected bone: to assess the local extent of the tumour.
• X-ray and CT scan of the lung: to detect any metastatic tumour in the lung.
• Isotope bone scan: to assess the local extent of the tumour and to detect any metastatic tumour in other bones.
• Bone marrow biopsy: to detect any metastatic tumour in the bone marrow.
• Magnetic resonance imaging (MRI) of the affected bone: may be complementary to CT scan.
• Biopsy of tumour and detailed pathological examination of the specimen: to provide an accurate diagnosis.

Treatment

The two goals of therapy, namely tumour control and preservation of function, determine the management of an individual tumour.  

The current treatment plans consist of chemotherapy plus radiotherapy or surgery. The purpose of chemotherapy is to eradicate the disseminated tumour cells and to shrink the local tumour. Chemotherapy is the most important component of treatment for Ewing's sarcoma because it greatly increases the chance of cure. Radiotherapy or surgery is used to secure local control of the tumour. Radiotherapy is usually preferred because it does not cause anatomical defects, in contrast to surgical resection. Surgical resection is applied only if there is an unmanageable fracture, or if the tumour arises at or below the knee in a young child, or if the surgical resection in a particular case causes only insignificant functional defects.

New forms of treatment, including bone marrow transplant, are being studied.

II. Osteosarcoma

Osteosarcoma is a type of malignant bone tumour in children. It accounts for 5% of all childhood cancer.

Most cases of osteosarcoma are found in patients between 10 to 25 years old.

Natural Development of the Disease

Osteosarcoma develops in the bone, usually the long bones. The most common sites are around the knee, at the lower end of the femur or the upper end of the tibia, and at the upper end of the humerus. It destroys the bone and invades the surrounding soft tissue.  It also spreads along the marrow cavity. Some patients may also have blood-borne tumour dissemination at the time of diagnosis. The most common sites of blood-borne dissemination are the lungs.

Symptoms

Persistent and localised pain is the most common complaint. Physical examination shows slight tenderness and a firm mass fixed to the bone, but the joint movements are usually normal. Sometimes, the bone may be weakened by the tumour so that it can fracture easily. Systemic symptoms such as fever or tiredness are rare.

Diagnostic Tests

The diagnostic procedures may include the following:

• Basic blood tests: to assess the vital functions of the body. 
• X-ray and CT scan or MRI of the affected bone: to assess the local extent of the tumour. 
• CT scan of the lungs: to detect any metastatic tumour in the lungs.
• Bone Scan: to assess the local extent of the tumour and to detect any metastatic tumour in other bones.
• Biopsy of the tumour: to establish the diagnosis.

Treatment

Modern treatment regimen for osteosarcoma consists of chemotherapy and surgery.

In the past, the limb bearing the tumour would be amputated. With the advance of surgical technique, it is now possible to perform limb-sparing surgery in which the tumour can be removed without amputating the limb. However, limb-sparing surgery cannot be performed if the tumour is too extensive, if there is infection in the affected bone, or when the tumour is in the lower limb of a very young patient.

After amputation or limb-sparing surgery, rehabilitation is essential to achieve maximum functional recovery. For most patients, they can adapt very well to their prosthetic limbs and return to full physical activity including sports.