Giant cell tumour of bone
Usually occurs after physeal closure and often reaches the subarticular epiphysis, commonly around the knee or distal radius.
Features:
- eccentric lytic lesion
- little matrix mineralisation
- can be locally aggressive
- pulmonary metastases are uncommon but possible despite benign histology
Treatment commonly uses extended curettage with local adjuvant techniques and cavity reconstruction. Wide resection is reserved for selected aggressive or unreconstructable disease.
Denosumab suppresses RANKL-driven osteoclast-like giant cells and has specialist indications; it is not a substitute for oncological planning.
Osteoid osteoma
- usually young patient
- severe nocturnal pain often relieved by NSAIDs
- small nidus with surrounding reactive sclerosis
CT best defines the nidus. Image-guided thermal ablation is commonly used for symptomatic accessible lesions.
Osteochondroma
A cartilage-capped exostosis with continuity of cortex and medullary canal with the host bone.
Operate for symptoms, mechanical problems, neurovascular compression, concerning growth after maturity or suspicion of malignant transformation.
An osteochondroma has continuity of cortex and medulla with the parent bone.
Concern for malignant transformation includes:
- new growth after skeletal maturity
- increasing pain
- thick cartilage cap
- destructive change
Enchondroma
Benign intramedullary cartilage lesion, common in the small bones of the hand and long bones. Distinguish from low-grade chondrosarcoma using symptoms, growth, cortical change and specialist imaging/pathology.
Multiple enchondromas occur in disorders such as Ollier disease; vascular lesions accompany enchondromatosis in Maffucci syndrome.
Common benign cartilaginous lesions may be incidental. Concern rises with:
- persistent attributable pain
- aggressive cortical change
- soft-tissue mass
- progression
- features suggesting chondrosarcoma
Fibrous dysplasia
Replacement of normal bone by fibro-osseous tissue. Can be monostotic or polyostotic. Proximal femoral deformity may produce a shepherd's-crook appearance.
Cystic lesions
- unicameral bone cyst: common in skeletally immature metaphyses and may present with pathological fracture
- aneurysmal bone cyst: expansile blood-filled lesion; may be primary or secondary to another tumour
Always confirm the diagnosis before treating a presumed benign lesion that has aggressive features.
Giant cell tumour
Giant cell tumour typically occurs after physeal closure and commonly involves the epiphyseal-metaphyseal region extending toward subchondral bone.
Radiographically it is usually:
- lytic
- eccentric
- relatively non-sclerotic at the margin
- potentially expansile and locally aggressive
It is histologically benign in most cases but can recur and rarely metastasise to lung.
Assessment
MRI defines local extent. Chest imaging may be considered because pulmonary metastases can occur despite benign histology.
Treatment
Extended curettage is commonly used for resectable lesions where the joint can be preserved.
Adjuncts may be used to reduce local recurrence, followed by defect reconstruction with cement and/or graft depending on site and strategy.
Wide resection is considered for selected very aggressive, recurrent or non-reconstructible lesions.
Denosumab can reduce tumour activity and is useful in selected cases, but its role around surgery requires specialist planning.
Simple bone cyst
Usually occurs in children and often affects proximal humerus or femur. It may present with pathological fracture.
Treatment depends on:
- symptoms
- fracture risk
- site
- age
- persistence
Aneurysmal bone cyst
ABC is an expansile blood-filled lesion that can be primary or secondary to another tumour.
Imaging may show expansion and fluid-fluid levels on MRI. Biopsy may be required because telangiectatic osteosarcoma can mimic ABC.
FRCS synthesis
“Benign” does not mean “ignore”. The correct approach is to identify whether a lesion is incidental, fracture-prone, locally aggressive or suspicious for malignant transformation.