Giant Cell Tumour

Definition & Epidemiology

Giant cell tumour (GCT, osteoclastoma) is a locally aggressive, usually benign tumour with a small but real potential for local recurrence and, rarely, pulmonary metastasis (‘benign metastasising GCT’) or malignant transformation. It characteristically occurs in young adults (20–40 years) after physeal closure and is located in the epiphysis/epi-metaphysis of long bones, most often the distal femur, proximal tibia (around the knee) and distal radius.

Clinical Features

Pain, swelling and reduced joint movement near a large joint in a young adult; a pathological fracture may be the presentation. Because the lesion reaches the subchondral bone, an effusion and joint symptoms are common. The clinical course is unpredictable: some lesions grow slowly over months while others enlarge rapidly and breach the cortex into the soft tissues.

Investigations

• Radiographs show a characteristic eccentric, expansile, purely lytic lesion in the epiphysis extending to the subchondral bone, with a ‘soap-bubble’ appearance, thinned or breached cortex and no surrounding sclerotic rim or matrix mineralisation.
• MRI defines soft-tissue extent
• CT chest is done because of the small risk of lung deposits.
• Biopsy shows a stroma of mononuclear cells with numerous evenly distributed multinucleated osteoclast-like giant cells.

Management

• Treatment is primarily surgical.
• Extended (aggressive) intralesional curettage — curettage with adjuvant measures such as a high-speed burr, and local adjuvants (phenol, hydrogen peroxide, or cryotherapy) — followed by filling of the cavity with bone cement (PMMA) or bone graft, is the usual approach, aiming to reduce the high recurrence rate while preserving the joint.
• Wide excision and reconstruction is reserved for extensively destructive or recurrent tumours.
• Denosumab (a rank-ligand inhibitor) is used for inoperable, axial or advanced disease. Radiotherapy is generally avoided (risk of malignant transformation).

Differential Diagnosis

An epiphyseal lytic lesion in a young adult should be distinguished from other subarticular lesions: chondroblastoma (typically before physeal closure, with matrix calcification), aneurysmal bone cyst (may coexist as a secondary change, fluid–fluid levels), a brown tumour of hyperparathyroidism (check calcium and PTH — an important mimic), and, when aggressive, a giant-cell-rich osteosarcoma. Correlation of age, site and biochemistry with histology resolves most cases.

Prognosis & Follow-up

Although histologically benign, GCT is locally aggressive and recurs in a significant proportion after intralesional treatment, usually within the first two to three years — hence the emphasis on extended curettage with adjuvants and on regular clinical and radiological follow-up, including chest imaging for the small risk of benign pulmonary ‘metastases’. Frank malignant transformation is rare and carries the prognosis of a sarcoma.

Benign but locally aggressive — can metastasise to lung rarely.

• Benign but locally aggressive; young adults after physeal closure; rare lung metastasis.
• Epiphyseal/subchondral around the knee & distal radius; eccentric expansile lytic ‘soap-bubble’.
• Numerous osteoclast-like multinucleated giant cells on histology.
• Extended curettage + adjuvants + cement/graft; wide excision if extensive/recurrent; denosumab for advanced.
• Avoid radiotherapy (malignant transformation); stage the chest.