Bone tumors
We can divide up bone tumors as follows:
- Fibrinogen
- Benign
- Simple cyst (can cause fractures)
- Aneurysmal bone cyst (cysts with blood inside - usually vertebral)
- Fibrous dysplasia (common 2nd -3rd decade)
- Fibrous cortical defect
- Malignant
- Malignant fibrosis
- Histiocytoma
- Fibrocystoma
- Chondrogenic
- Benign
- Enchondroma (tumours of hyaline cartilage, may be on epiphysis of bone or periosteum, malignant transformation has been seen - excise and graft).
- Periosteal chondroma
- Osteochondroma (most common benign bone tumour, can transform to malignant)
- Chondromyxoid fibroma
- Chondroblastoma (common in knee, hip and shoulder joints, usually involves physis)
- Malignant
- Chondrosarcoma
- Osteogenic
- Benign
- Osteoid osteoma (commonly femur, tibia and vertebrae, px have pain that is worse at night, generally self limiting).
- Osteoblastoma (commonly in posterior spine and skull)
- Ossifying fibroma
- Malignant
- Osteosarcoma
- Unknown origin
- Benign
- Giant cell
- Malignant
- Ewing’s sarcoma
- Synovial sarcoma
- Bone marrow
- Malignant
- Myeloma
- Lymphoma
First let's review some important benign bone tumours.
Osteoid osteoma
Commonly affects males between the ages of 10-25, presents with severe and persistent pain, commonly affecting femur and tibia (although spinal peduncle can be a site as well). The lesion is found in the cortex of the bone and it causes reactive sclerosis. Surgical excision is curative.
Chondroma
The most common of all bone tumours, and it often first presents as a pathologic fracture. There are two variants, the enchondroma (confined within cortex) and the ecchondroma (protrudes beyond the cortex). These tumors most commonly occur in tubular bones of the hands and feet and rarely in the long bones. Malignant transformation can occur in about 25% of cases.
Osteochondroma
Typically occurs on the external surface of a metaphysis (usually the distal femur, proximal humerus or proximal tibia) and it is thought that it is the result of failure of remodeling during growth that leads to a pedunculated growth arising from the metaphysis. These are often asymptomatic for many years although they can stop proper bone maturation and so should be treated suspiciously.
Below we consider in detail some of the more important malignant bone tumours.
Osteosarcoma
These are the most common malignant tumours in bone and have a low survival rate, they are commonly found in teenagers and young adults. It exhibits osteoblastic differentiation and produces malignant osteoid tissue. There is a genetic component to its formation, but risk factors include Pagets and other bone dysplasias. Osteosarcomas tend to be found at sites of bone growth.