Bones are a common site of secondary metastatic disease; most commonly from lung, breast, prostate, and renal primaries. Metastatic disease spreading to bone may be solitary, multifocal, or diffuse (seen throughout the skeleton). Metastatic bone lesions may be sclerotic (increased bone density) or lytic (reduced bone density).
Imaging of Musculoskeletal Disorders
Bone tumours - Secondary
Key points
- Bone metastases may be solitary, multifocal, or diffuse
- Bone metastases may be sclerotic or lytic
Sclerotic bone metastasis – Solitary
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Sclerotic bone metastasis – Solitary
- A solitary area of sclerosis (increased bone density) is seen in the pelvis of this patient with metastatic breast cancer
Sclerotic bone metastases – Diffuse
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Sclerotic bone metastases – Diffuse
- All the bones of this man with metastatic prostate cancer are very sclerotic
- (The overlay image shows normal bone density in a normal subject for comparison)
Lytic bone metastasis – Solitary
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Lytic bone metastasis – Solitary
- A focus of low density is seen within the bone marrow of the femur
- The upper and lower edges are poorly defined (wide zone of transition)
- This was a lytic (bone destructive) lesion in a patient with lung cancer
Lytic bone lesions - Multiple myeloma
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Lytic bone lesions - Multiple myeloma
- Multiple myeloma is a disease which commonly presents with multiple lytic bone lesions at the time of diagnosis
- Strictly speaking these are not metastases but rather the manifestation of multiple lesions arising throughout the axial skeleton
- Lesions arise from bone marrow and cause characteristic ‘punched-out’ lytic foci
Other imaging modalities
Other imaging modalities such as CT, MRI, and Nuclear Medicine Bone Scans may be helpful in the management of patients with bone tumours.
Bone metastasis – CT
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Bone metastasis – CT
- This CT of the thoracic spine shows a focal lytic lesion which has destroyed the transverse process of the vertebra at this level
- CT is often used to help guide percutaneous needle biopsy of bone lesions
- Multiple myeloma was diagnosed following biopsy in this case
Metastases – MRI
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Metastases – MRI
- This MRI demonstrates diffuse abnormality of the bone marrow of the spine in this man with prostate cancer
- Both of these scans are T1-weighted images (fatty tissue in the bone marrow should be bright – see the normal image shown for comparison)
- In the image on the right, tumour cells have replaced the normal fatty bone marrow of the spine resulting in a loss of bone fat signal due to bone oedema – the vertebral bodies are much darker than in the normal subject (arrows)
Metastases – Bone scan
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Metastases – Bone scan
- If the diagnosis of bone metastasis is suspected, or if an aggressive bone lesion is found in one location, then a bone scan can be used to determine how widespread disease has spread to the rest of the skeleton
- In this patient with known prostate cancer the bone scan shows widespread abnormal uptake of radionuclide marker indicated by the black areas (marked red on the overlay image)
- Note: Bone scans are not sensitive for the detection of all malignancies of bone. For example, bone scans are frequently negative in cases of multiple myeloma.
Pathological fractures
Pathological fractures arise as a result of alteration to bone structure due to any disease process within bone, including benign tumours, and malignant primary or secondary bone tumours. They can occur following trivial trauma.
Note: Pathological fractures also occur in osteoprotic bones.
Pathological fracture – Lesser trochanter
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Pathological fracture – Lesser trochanter
- There are patchy areas of increased density (sclerosis) and decreased density (lysis) resulting in a ‘moth-eaten’ bone texture in the pelvis and proximal femur
- The lesser trochanter is detached – this is the site of insertion of the iliopsoas tendon
- This injury is rarely seen in the absence of bone metastases