Osteosarcoma is the most common sarcoma of the bone in all age groups. In paediatrics, the management has changed significantly over the past 50 years with the development of effective systemic therapies that have lead to limb-sparing procedures. The usual presenting symptoms have not changed, although the advent of CT and MRI imaging has led to improved pre-operative staging and decision making.
History
Presenting Complaint
Most patients present with symptoms related to the site of disease over a period of weeks to months. The characteristic complaint is of pain; in the early stages of disease it may be relapsing-remitting but becomes constant over time. The most commonly involved sites are:
- The femur (40%)
- The tibia (15%)
- The humerus (15%)
The metaphysis is the most commonly involved site (over 90% of cases). Most other cases occur in the diaphysis. The epiphysis is very rarely the site of disease but may be involved by locally advanced tumour.
Although there may be a history of trauma prior to development of symptoms, there is no evidence that trauma per se leads to osteosarcoma; rather it is thought that the trauma makes the patient aware of the site of disease.
Past Medical History
In children there is usually no other past history of note. Two important genetic syndromes place children at higher risk:
- Hereditary Retinoblastoma, due to germline mutation of RB1, places patients at high risk for many cancers but especially retinoblastoma and (if they survive) osteosarcoma
- Li-Fraumeni Syndrome, due to germline mutation of TP53, also increases the risk of many cancers including osteosarcoma.
In adults, a history of previous radiotherapy or Paget's disease of bone place them at higher risk of osteosarcoma. These factors are not usually important in children.
Paediatric History
Medications
Nil specific
Allergies
Nil specific
Family History
A family history of hereditary malignancies due to mutation of TP53 or RB1 should be inquired after.
Social History
As with all paediatric malignancies, the social history is of significant importance, including:
- Family makeup (parents, siblings, other relatives)
- Stage of schooling (pre-school, primary school, secondary school)
- Drug and alcohol use
- Other supports
Important History Questions
- Other sites of pain
- Family history of retinoblastoma, sarcoma or hereditary cancers
- Social history (paediatric patient)
Examination
Examination should be focused on the primary site as well as on detection of metastases. The primary tumour site often demonstrates a mass which is usually tender. Other findings include limitation of movement of the involved bone/joint, increased warmth of the region and rarely an audible bruit.
Regional nodes are not usually involved.
The tumour typically spreads to the lungs but may spread to other bones in the terminal phases of the disease. Lung metastases, if extensive, may be detected on clinical examination.
Blood Tests
Blood tests are usually unhelpful in diagnosis but may provide markers for disease progression (e.g. ALP)
Imaging
Plain X-Ray
Conventional radiographs may demonstrate a variety of appearances, with osteolytic or osteoblastic areas (or both). Typically there is a mixed picture, giving the classical cumulus cloud pattern. Pathological fractures may be visible.
WBBS
Most osteosarcomas take up 99Tm tracer, with close to 100% sensitivity. Specificity is worse but WBBS is useful in detecting other sites of bony disease.
CT & MRI
CT and MRI have revolutionised the treatment planning of osteosarcoma. They allow assessment of the extent of disease within the bone, as well as of extension into surrounding soft tissue.
Staging
Osteosarcoma is staged with the TNM System. The grade of the tumour is always included in this system.
T Stage:
- T1: Tumour ≤ 8 cm
- T2: Tumour > 8 cm
- T3: Discontinuous tumours in the primary bone site
N Stage:
- N1: Regional nodal metastases
M Stage:
- M1a: Lung metastases
- M1b: Other distant metastases
Grade:
- G1: Well differentiated / low grade
- G2: Moderately differentiated / low grade
- G3: Poorly differentiated
- G4: Undifferentiated
Overal TNM Stage
| Stage | T | N | M | Grade |
|---|---|---|---|---|
| IA | T1 | N0 | M0 | G1-2 |
| IB | T2-3 | N0 | M0 | G1-2 |
| IIA | T1 | N0 | M0 | G3-4 |
| IIB | T2 | N0 | M0 | G3-4 |
| III | T3 | N0 | M0 | G3-4 |
| IVA | TAny | N0 | M1a | GAny |
| IVB | TAny | N1 NAny |
MAny M1b |
GAny |
