Imaging of Musculoskeletal Disorders
Bone tumours - Primary

Key points

  • Benign and malignant bone lesions are not always distinguishable with imaging
  • Lesions are described as having aggressive or non-aggressive features
  • Aggressive features can be similar to the changes seen in osteomyelitis

Imaging techniques cannot always distinguish between malignant tumours and other aggressive lesions of bone, such as osteomyelitis. Therefore, the terms ‘benign’ and ‘malignant’ are best avoided when describing possible bone tumours. Rather, the terms ‘aggressive lesion’ and ‘non-aggressive lesion’ are frequently used to describe imaging features of suspected bone tumours.

Features which would favour an aggressive lesion, such as cancer or infection, include a wide ‘zone of transition’ and 'periosteal reaction'.

Zone of transition

The zone of transition is the point at which normal bone can be distinguished from abnormal bone.

Narrow zone of transition – Non-ossifying fibroma

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Narrow zone of transition – Non-ossifying fibroma

  • This bone lesion has a narrow zone of transition – a well-defined thin rim of sclerosis separating normal and abnormal bone
  • This is a non-aggressive feature
  • These are the typical appearances of a non-ossifying fibroma – a developmental abnormality
  • Note: This asymptomatic bone abnormality was discovered incidentally following an ankle injury

Wide zone of transition – Osteosarcoma

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Wide zone of transition – Osteosarcoma

  • The bone texture is very abnormal distally – the normal trabecular pattern is replaced by small irregularly-shaped holes
  • The term ‘moth-eaten’ is often used to describe this type of abnormal bone texture
  • The bone texture appears normal more proximally
  • It is not possible to define a point at which normal bone becomes abnormal – the ‘zone of transition’ is wide
  • Biopsy proved this bone lesion to be a primary osteosarcoma
  • (Same patient as image below)

Periosteal reaction

The periosteum reacts to the presence of aggressive bone lesions by laying down abnormal new bone. The presence of ‘sunburst’ periosteal reaction (irregular frond-like thickening of the cortex), or a ‘Codman’s triangle’ (thickened cortex lifting away from the bone) are features associated with high likelihood of a primary bone malignancy.

Periosteal reaction – Osteosarcoma

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Periosteal reaction – Osteosarcoma

  • (Same patient as image above)
  • Periosteal reaction is an aggressive feature seen in malignant bone disease and infection
  • Sometimes periosteal reaction has a ‘sunburst’ appearance
  • Periosteal reaction may also result in the appearance of a triangle of new bone seen lifting away from the cortex surface (Codman's triangle)
  • Sunburst and Codman's triangle periosteal reaction are aggressive features associated with high likelihood of a malignant process

Page author: Salisbury NHS Foundation Trust UK (Read bio)

Page edited by: Dr Richard Smith BSc MSc MBBS FRCP PGDip - Consultant Rheumatologist (Read bio)

Last reviewed: January 2020