Giant Cell Tumor

Epidemiology

Giant cell tumors account for approximately five percent of all primary bone tumors.
Most commonly affect patients between twenty and forty years of age.
There is a slight female predominance.
Tumors usually present as solitary lesions.
Multicentric giant cell tumors are rare, occurring in one to two percent of cases, and may be synchronous or metachronous.

Common Anatomical Sites

Distal femur is the most common site of involvement.
Proximal tibia is the second most frequent location.
Distal radius is the third most common site and is often more aggressive.
Involvement of the spine is uncommon, except for the sacrum.
In skeletally immature patients, lesions are typically located in the metaphysis rather than the epiphysis.

Biological Behavior

Giant cell tumors are generally benign but locally aggressive.
Most tumors present as stage two or stage three lesions.
Pulmonary metastases occur in approximately three percent of patients.
Mortality among patients with lung metastases is approximately fifteen percent.
Malignant transformation occurs in fewer than five percent of cases.

Malignant Giant Cell Tumors

Primary malignant giant cell tumor:
- Sarcoma arising de novo within a typical benign giant cell tumor.
- Extremely rare.
Secondary malignant giant cell tumor:
- Sarcoma developing after treatment of a benign giant cell tumor.
- Most commonly associated with prior radiation therapy.

Clinical Presentation

Progressive pain is the most common symptom.
Pain initially occurs with activity and later becomes present at rest.
Pain is usually mild to moderate unless complicated by a pathological fracture.
Pathological fractures are present at diagnosis in ten to thirty percent of patients.
Local swelling or deformity may be seen in advanced cases.

Radiographic Features

Eccentric, osteolytic lesion involving the epiphysis of long bones.
The lesion typically extends to and abuts the subchondral bone.
Aggressive lesions show a poorly defined zone of transition.
Less aggressive tumors may show a partial rim of reactive bone.
Cortical thinning, expansion, or breach is common.
Intra-articular extension is rare.

Magnetic Resonance Imaging Characteristics

T1-weighted images show low signal intensity.
T2-weighted images show high signal intensity.
Magnetic resonance imaging is useful for assessing:
- Intraosseous extent
- Soft-tissue involvement
Fluid–fluid levels suggest a secondary aneurysmal bone cyst, seen in approximately twenty percent of cases.

Histopathology

Numerous multinucleated giant cells, often containing forty to sixty nuclei per cell.
Giant cells are distributed within a background of mononuclear stromal cells.
The nuclei of giant cells and stromal cells are morphologically identical, which is diagnostic.
Additional features may include:
- Reactive bone formation
- Foamy macrophages
- Secondary aneurysmal bone cyst changes
Histological grading does not correlate with prognosis.

Natural History and Recurrence

Historically, recurrence rates exceeded fifty percent following simple curettage.
Modern extended curettage techniques have reduced recurrence to five to fifteen percent.
Risk of pulmonary metastasis is higher in:
- Stage three tumors
- Recurrent lesions

Principles of Surgical Management

Extended intralesional curettage is the treatment of choice.
A large cortical window should be created to visualize the entire tumor cavity.
A high-speed burr is used to extend the margins by one to two centimeters.
Care must be taken to avoid damage to the subchondral bone.

Adjuvant Therapies

Adjuvants are used to eradicate residual tumor cells after curettage.
Commonly used adjuvants include:
- Argon beam coagulation
- Electrocautery
- Bone cement
Phenol and liquid nitrogen are avoided in some centers due to risk of complications.
Bisphosphonates may reduce recurrence by inhibiting osteoclastic activity.

Defect Reconstruction Options

Autologous bone graft
Allogeneic bone graft
Bone graft substitutes
Polymethyl methacrylate bone cement

Advantages of Bone Cement

Provides immediate mechanical stability.
Allows early mobilization and rehabilitation.
Facilitates early detection of recurrence as radiolucency at the cement–bone interface.
Heat generated during polymerization may destroy residual tumor cells.

Augmentation Techniques

Crossed or divergent screws can be placed within the cement mantle.
This significantly improves the biomechanical strength of the reconstruction.

Indications for Wide Resection

Aggressive stage three lesions.
Recurrent tumors.
Tumors unresponsive to intralesional management.

Site-Specific Surgical Options

Around the knee:
- Hemicondylar allograft reconstruction
- Rotating hinge endoprosthesis
Distal radius:
- Resection with proximal fibular autograft
- Arthroplasty or arthrodesis
Expendable bones:
- Resection without reconstruction
Spine and pelvis:
- Embolization or radiation therapy for inoperable lesions

Medical Management

Bisphosphonates:
- Used systemically or locally
- Evidence for efficacy is still evolving
Denosumab:
- Receptor activator of nuclear factor kappa-B ligand inhibitor
- Approved for unresectable tumors or cases with high surgical morbidity
- Leads to sclerosis, cortical reconstitution, and pain reduction
- Long-term outcomes remain under evaluation

Management of Pulmonary Metastases

Surgical resection is preferred when feasible.
Chemotherapy has limited effectiveness.
Radiotherapy is reserved for symptomatic, unresectable disease.

Follow-Up Protocol

Long-term surveillance is essential due to risk of late recurrence.
Chest radiography and computed tomography are performed at diagnosis for staging.
Follow-up imaging schedule:
- Every three to four months for the first two years
- Every six months during the third year
- Annually thereafter
Magnetic resonance imaging is indicated when soft-tissue recurrence is suspected.

Management of Recurrence

Managed similarly to primary tumors.
Histologically benign recurrence:
- Repeat extended curettage or resection
Malignant transformation:
- Requires oncologic wide resection

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