Giant cell tumour
Overview
- Intermediate (locally aggressive) tumour in WHO classification
- Composed of mononuclear stromal cells and multinucleated giant cells (functionally resemble osteoclast)
- Rarely metastasises (lung mets in ~2–5% despite benign histology)
Epidemiology
- Age: 20–40 years (skeletally mature) but older age can also be seen (may be due to late presentation?)
- Slight female predominance
- Accounts for ~5% of primary bone tumours (relatively common)
Common Locations
- Epiphysis or metaphyseal-epiphyseal junction of long bones
- Very rare before physeal closure - in an open physis, an epiphyseal lesion is Chondroblastoma until proven otherwise.
- Most common sites:
- Knee: distal femur > proximal tibia
- Distal radius (tends to recur more, functionally more aggressive)
- Sacrum (axial variant): often difficult or impossible to resect en bloc
Clinical Features
- Local pain and swelling
- Limited joint mobility (due to juxta-articular location)
- Possible Pathological fracture
- Rare lung metastases (despite benign histology)
Histology
- Numerous uniformly distributed multinucleated giant cells
- Background of mononuclear stromal cells (neoplastic component)
- Most conventional giant cell tumours harbour an H3F3A mutation (G34W), which helps distinguish them from other giant-cell–rich lesions.
- May show areas of haemorrhage, necrosis, or cystic change
Imaging Features
Radiograph
- Eccentric, expansile, lytic lesion
- Can extend to subchondral bone (epiphyseal involvement is classic)
- Non-sclerotic margin, narrow zone of transition (modified Lodwick 1B)
- Periosteal reaction is usually absent unless there is a Pathological fracture.
- No matrix mineralization
- Soft tissue mass suggests more aggressive or recurrent disease.
MRI
- T1: Iso to hypointense
- T2: Variable (often heterogeneous hyperSI)
- Peripheral low-signal rim may reflect sclerosis/hemosiderin
- May show fluid-fluid levels (especially if secondary ABC)
- Enhancing solid components and internal septations
- Useful for assessing soft tissue extension
CT
- More detailed evaluation of cortical destruction and internal trabeculae
- Helpful for surgical planning
Differential Diagnosis
Practically, well-defined non-sclerotic rim osteolytic lesion with "3E" features (epiphyseal involvement, eccentric, expansile) without matrix mineralization in skeletally mature patient is very suggestive of giant cell tumor.
But nevertheless, let's provide some possible differential for completeness.
| Diagnosis | Key Differences |
|---|---|
| Chondroblastoma | Younger patients, epiphyseal, smaller, stippled calcified matrix, chicken-wire calcification |
| Aneurysmal bone cyst (ABC) | Younger age, fluid-fluid levels dominant, metaphyseal location |
| Brown tumour | Types of hyperparathyroidism, multifocal, lab abnormalities |
| Telangiectatic Osteosarcoma | Aggressive, permeative margins, malignant soft-tissue mass, fluid-fluid levels, malignant cells producing osteoid matrix, giant cells may be present but not uniform like GCT |
| Giant cell-rich osteosarcoma | Atypical age, malignant features, osteoid matrix |
Management
Resectable
- Extended curettage ± adjuvant (e.g., phenol, cryotherapy) with cement or bone graft
- Wide excision for recurrent or aggressive lesions
Unresectable
- Radiotherapy: used cautiously because of risk of secondary sarcoma.
- Denosumab (RANKL inhibitor): used for unresectable/sacral lesions or as neoadjuvant. It induces peripheral sclerosis and can obscure the true tumour margin on imaging and at surgery.
Prognosis
- High local recurrence rate after curettage
- Good with adequate local control (wide resection with R0 margin - at the cost of function)
- Lung metastases are rare, often indolent; some may remain stable or even regress spontaneously.
Practical pearls
- Absence of matrix calcification and non-sclerotic margin are key clues.
- May show fluid-fluid levels — but don't call it ABC or telangiectatic Osteosarcoma purely on that.
- Always distinguish from Chondroblastoma (younger age, skeletally immature) and brown tumour (check hyperparathyroid labs).
- If it’s epiphyseal, skeletally mature, non-sclerotic, no matrix, ‘3E’ (epiphyseal, eccentric, expansile) → giant cell tumour until proven otherwise.
