Bone Lesions/Tumours

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Bone Lesions/Tumours

Evaluation and classification of bone lesions/tumours:
1) Where does it originate from (eg medullary, cortical, metaphyseal)
2) The presence of any new bone growth
3) The presence of any bone destruction
4) The extent of soft tissue invasion
5) Is the lesion ‘expansile’?
6) Border – sharp line of demarcation or irregular/ill-defined border
7) Is cortex disrupted?
8) Single or multiple

General characteristics of benign/slow growing lesions
Generally smaller, well demarcated, cortical margins are preserved and sclerotic, usually trabeculated, uninterrupted periosteal reaction

General characteristics of malignant/fast growing lesions
Generally larger, ill-defined margins, cortical erosions or destruction, periosteal reaction, wide zone of transition into surrounding soft tissues, no sclerosis of margins, appear ‘moth eaten’ or permeative

Appearance of the periosteum in response to a bone tumour:
• Buttressing – the periosteum thicken in response to a slow growing tumour
• Sunburst – ‘ray’ are seen projecting from the periosteum; eg haemangioma, Ewing’s sarcoma, osteogenic sarcoma
• Codman’s triangle – triangle shaped elevation of the periosteum; eg osteogenic sarcoma
• Hairy – similar to sunburst, but rays are parallel and project at right angles from periosteum; eg Ewing’s sarcoma
• Onion skin – multiple layers of periosteal new bone formation

Appearance/Pattern of bone destruction in response to a bone tumour:
• Geographic – has well defined margins; short zone of transition from the normal to the abnormal bone; indicates a slow growing lesion
• Motheaten – margins are less well defined; larger zone of transition between normal and abnormal bone; indicates a more aggressive lesion than the geographic pattern
• Permeative – very poorly defined margins; large zone of transition between normal and abnormal bone (may not be able to determine a boundary); very aggressive fast growing lesions

Mnemonic for the differential diagnosis of solitary lucent bone lesions – FOGMACHINES:
Fibrous dysplasia, Osteoblastoma, Giant cell tumour, Metastasis/Myeloma, Aneurysmal bone cyst, Chondroblastoma/Chondromyxoid fibroma, hyperparathyroidism (brown tumours)/Hemangioma, Infection, Non-ossifying fibroma, Eosinophilic granuloma/Enchondroma, Solitary bone cyst

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