Metastatic Bone Disease: A Brief Overview
Malignant metastatic bone disease arguably represents the most common sinister condition presenting in practice. Its various forms are characterized radiographically by lesions with ill-defined margins – wide zone of transition – variations in size, haphazard asymmetrical distribution, and, with progression, loss of cortical integrity and/or pathological fractures.
Figure 1 demonstrates universal mixed metastatic disease seen throughout the entire visualized skeleton. Note the various patches of ill-defined sclerosis adjacent to ill-defined regions of rarefaction, all of varying size, and asymmetrically distributed. Although spread throughout every bone seen here, observe the total maintenance of each joint space. (Differential diagnosis: aggressive infectious process.)
Some Points to Remember About Metastatic Disease
- most metastases to bone arises from a primary carcinoma in a patient over 40 years of age
- may produce an osteolytic (75 per cent), osteoblastic (15 per cent) or mixed (10 per cent) pattern
- prostate and lung are most common primary sites in males
- lung and breast are most common primary sites in females
- 80 per cent of osteolytic metastasis occurs in the axial skeleton: back pain is often the presenting complaint of a patient with an undetected primary malignant tumour that has metastasized to the spine
- it is therefore prudent to consider metastatic bone disease in the differential diagnosis of a patient over 40 presenting with unexplained back pain
- there is usually no periosteal response (differential diagnosis: primary bone neoplasm)
- metastasis is rare distal to the elbow or knee
- a lesion requires 30 to 50 per cent bone destruction to be visualized on plain film
- bone scan (scintigraphy) is 10 times more sensitive than plain film
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