Bone Metastasis from Lung CA

Lytic Destruction of Left Sacral Wing and Ilium

• Close inspection of the left sacral wing reveals absence of the neural foramena and lateral margin.
  • The pelvic ring is incomplete posteriorly on the left, implying adjacent left iliac bone destruction.
• Oblique view of the pelvis demonstrates the destructive changes more clearly.
• CT of the lumbosacral spine barely extends inferiorly to include the left sacral wing and iliac destruction.
• Nuclear Medicine bone scan confirms the left sacral wing abnormality and detects post surgical changes in left ribs s/p lobectomy (evident on chest x-ray).
• A composite image may clarify the relationship among the imaging modalities.

• The history of lung CA was omitted from the x-ray request!

The combination of radiographic findings is consistent with lytic destruction of the left sacral wing and and adjacent left iliac bone from metastatic lung carcinoma.

• The pelvis is notoriously difficult to evaluate because of complex three dimensional relationships.
  • For this reason, multiple views (inlet, outlet, oblique, Judet, etc.) are available provided the index of suspicion is high.
  • CT scans are excellent for depicting pelvic bone anatomy.
  • CT, ultrasound and MR are useful for evaluating pelvic contents.
• Unfortunately, none of these may come into play unless the x-ray of pelvis is interpreted correctly.

• The differential diagnosis includes:
  • Chordoma -- rare primary tumor of notochordal origin.
  • Chondrosarcoma.
  • Multiple myeloma.
  • Giant cell tumor.
  • Metastatic disease.

Ref: Resnick, D., Bone and Joint Imaging, W.B. Saunders, Philadelphia, PA., 1989

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