Bone tumors may be benign or malignant. Benign tumors enlarge slowly, and do not cause danger to life or limb. Malignant tumors are cancerous, and may spread by the blood stream to other parts of the body.

Examples of benign tumors are as follows.

• Nonossifying fibroma or fibrous cortical defect is a common tumor, which is usually incidentally found on X-rays taken to rule out fractures in children. Unless they are large and weaken the bone sufficiently to cause a fracture, they can be left alone. If it involves more than 50% of the diameter of a long bone, excision and curettage is advised to prevent fractures from happening.

• Unicameral bone cyst or solitary bone cyst occurs anywhere in the skeleton, but commonly in the upper part of the humerus (upper arm) and upper part of the femur (thigh bone). It has a characteristic appearance on X-ray, and does not require any treatment if small. It causes symptoms only if it gets large enough to cause weakness in the bone, resulting in a fracture. When that occurs, treatment is usually directed towards the fracture. Frequently, with the bleeding from the fracture occuring in the cyst, the fracture heals and obliterates the cyst. If the cyst persists even after the fracture heals, it is advisable to excise the cyst and bone graft it to prevent future fractures.

• Aneurysmal bone cyst (ABC) can occur anywhere in the body, but commonly in the posterior part of the spine, and the long bones. It has a typical expansile appearance on X-rays. It can cause pain, and requires curettage (scraping it out with a spoon-like instrument) or excision and bone grafting. Sometimes the tumor recurs after curettage.

• Osteochondroma or exostosis occurs commonly in the long bones around the major joints like the knee. Typically, the patient can feel a bony lump arising from the bone near a joint. It is typically painless unless it abuts on a nerve. X-rays have a typical appearance, and does not need excision unless it is getting larger, or causes symptoms. In some children, this tumor occurs at multiple sites in the body (a condition called hereditary multiple exostosis). In these cases, there is a 1% chance of malignant change, and so needs careful observation.

• Eosinophilic granuloma or Histiocytosis X occurs anywhere in the body, but commonly in the skull. Very often, it involves multiple systems and organs of the body.

• Fibrous Dysplasia commonly involves the skull, ribs and long bones and has a typical "ground glass" appearance on X-rays. It can cause pain if large, and needs curettage and bone grafting.

• Chondroblastoma typically affects the epiphysis of the growing skeleton (the growing part), which makes treatment more complicated than most. Fortunately it is very rare.

• Enchondroma is a cartilage tumor that occurs within the long bones of the limbs and fingers, Sometimes it occurs in multiple sites, and is called Ollier's disease.

• Chondromyxoid fibroma is a bening tumor that occurs in the shaft of the long bone. It frequently causes pain and swelling. Treatment is by curettage and bone grafting. Local recurrence after surgery can occur.

• Osteoid osteoma is a small painful lesion, typically causing pain at night relieved by Aspirin. It can occur anywhere in the body, but commonly in the long bones and the spine. Diagnosis is by its typical appearance of a small dense lesion on X-rays. CT scan may be needed to delineate the lesion. Treatment is usually excision.

• Osteoblastoma is a small painful lesion, usually affecting the spine. Treatment is by excison and bone grafting.

• Ewing's Sarcoma can occur anywhere in the body, and is very aggressive in its spread to the rest of the body. Treatment is by chemotherapy.

• Osteosarcoma occurs typically around the knee. It usually causes pain, and may be associated with a pathological fracture. Treatment consists of chemotherapy and surgery. Recent advances have improved 5-year survival to 70%. Limb sparing operations are also increasingly successful with more potent chemical agents.

• Leukemia can present as bone pain, although blood tests will confirm the diagnosis.