Name: Classic Osteosarcoma - Osteosarcoma - Orthofracs
Published: 2020-04-20T12:07:14+00:00

Epidemiology

Children
- Most common, high grade, central, affects children
- 85% of osteosarcomas
M:F – 1.5:1
Location
- 90% in ends of long bones
- 50% around knee
- distal femur 34%
- proximal tibia 17%
- femoral shaft 5%
- proximal femur 5%
- proximal humerus 9%

Clinical Features

Dependent on predominant type of matrix produced
Lichenstein’s classification
- Conventional
  - Bony (50% of all central OS)
  - Cartilaginous
  - Fibrous
- Telangiectactic
- Small cell
- Giant cell (fibrohistiocytic)
Therefore gross & micro appearance varies
Osteosarcoma is the great histological imitator among bone tumours just as Ewings sarcoma is the great radiological imitator among bone tumours

Diagnosis depends on production of malignant osteoid by the tumour
Cellular areas with microscopic trabeculae of bone between cells
Pleomorphic spindle cells with
- Hyperchromatic nuclei
- Atypical mitotic figures
- May also see anaplastic cell matrix & mix of fibrous, cartilaginous & bony tissues

Conventional form
- Osteoblastic
  - Prominent osteoid
- Chondroblastic
  - Prominent cartilage
- Fibroblastic
  - Prominent fibrous tissue
  - Looks like fibrosarcoma
Telangiectatic form (< 5%)
- Similar to ABC
- Large lytic defect filled with blood filled cavity
- Dilated vascular channels with multinucleated giant cells
- Anaplastic sarcomatous stroma with bone formation
- Worse prognosis than conventional form
Small cell form
- Similar to Ewing’s sarcoma
- Nests of small cells with spindle arrangement
- Sparse osteoid
- Worse prognosis than conventional form
- Responds to chemotherapy like PNET
Fibrohistiocytic variant (giant cell variant)
- Similar to MFH
- Higher age group in 3rd decade
- Pleomorphic spindle cells & multinucleated giant cells
- Osteoid with inflammatory matrix

Primarily haematogenous
- Lung mets can be treated by chemotherapy & surgical excision
- Bone mets have very poor prognosis
Up to 80% have at least micrometastatic spread on presentation
Multifocal OS very rare (? actually represents metastatic OS)

Definitive Diagnosis in 55%
Differential Diagnosis in 35%
Wilner’s classification
- Sclerotic 30%
- Lytic 20%
- Mixed 45%
Central & destructive lesion in metaphysis
- Involves medullary canal
- Lytic & Blastic
- Permeative cortical destruction
Periosteal reaction of rapid growth
- Codman’s Triangle (benign reactive bone which should be avoided in biopsy)
- Sunburst Spicules
- Soft tissue component
- Fluffy neoplastic bone
Rarely in diaphysis or even epiphysis
Soft tissue extension the rule

Defines extraosseous component
Identifies neoplastic bone in soft tissues
CT lung
- 10% of patients have pulmonary mets on presentation
- Best resolution for metastases

Identifies
- Skip lesions
- Metastases
- Polyostotic disease
- Pulmonary metastases

Systemic treatment
Goals of chemotherapy
- Shrink tumour size
- Treat micrometastases
- Assess tissue response
- Allow Limb Salvage Surgery (LSS)
- Time to manufacture custom prosthesis
Neoadjuvant & Adjuvant (pre & post-op chemotherapy)
- Marked improvement in the 5 year survival rates with this
- Response to chemotherapy best indicator of survival
- Necrosis Response (Huvos Grade: Grade 1 < 50%, Grade IV > 90%)
  - > 90% necrosis correlates with good prognosis
  - Greater the necrosis » better the survival
- Some osteosarcomas have P-Glycoprotein Pump
  - Which removes chemotherapy from the cell
2 cycles Preoperative
- Rosen T 10 Regime outdated
- Current regimen “MACI”
  - MTX
  - Adriamycin
  - Cisplatin
  - I-Phosphamide
Postoperative regimen
- Similar
- Can add VP16 & CPM (? Only if surgical excision shows > 10% tumour viability)

Usually 3/12 after diagnosis
Usually 2/52 after end neoadjuvant chemotherapy
Consists of wide excision
- 7cm proximally, 5cm distally
- Can be in form of amputation or limb salvage procedures
Reconstructive Technique
- Endoprosthesis ~ Best Results
- Arthrodesis
- Allograft
- DXRT to prevent local recurrence
- Adjuvant Chemotherapy for systemic treatment
Reasons for amputation
- Soft-tissue & neurovascular involvement
- Gross leg-length inequality (young child)
- Infected tumour
- Unstable pathological fracture
- Disadvantaged situation (environment, patient variables)
Poor outcome with any local recurrence after surgery
Poor outcome in presence of pathological fracture
Isolated Lung metastasis can be resected with good long term outcome

Prior to 1971
- 20% 5 year survival rate
Now
- 70% 5 year survival rate (80% some centres)
Due to
- Improved resection techniques
- Adjuvant chemotherapy (Mayo clinic – 40% 5 year survival without chemo)
- Resection of lung metastases early (some thoracic surgeons happy to do multiple metastectomies for osteosarcoma)
Limb salvage now viable option
- Local recurrence rate the same in distal femoral OS with limb salvage vs AKA
  - 74% LSS vs 64% amputation at distal femur
- Local recurrence rates are the same at 5-10%
Local Recurrence
- Incidence 5-10%
- Survival 5-10% at 5 years
- Treat with local measures only
- Dickinson says » recurrence = death
Worse prognosis if
- > 15cm (3x)
- Symptoms < 6/12
- Age < 10 years
- Males
- Elevated ALP & LDH
- Osteoblastic/ Chondroblastic
- Proximal or Central lesion
- Pathological fracture
- NV involvement
Late Presenter
- Paradoxically better survivor
- Less aggressive tumour
- Main indicator of survival is nature of tumour
  - Rather than nature of treatment
Death due to
- Local recurrence
- Lung secondaries

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.