April 2, 2009

FDG-PET: False Positive for Cancer

Fig. 1: Scout CT image shows a right hilar mass with right upper lobe opacity and volume loss. Findings are concerning for obstructive pneumonia due to carcinoma in the right hilum.
Fig. 2: Axial CT image shows right hilar lymphadenopathy (arrow) with consolidation, air bronchograms and cavities in the posterior segment of the right upper lobe (star)
Fig. 3: FDG-PET image shows markedly increased uptake of the right upper lobe consolidation, however the right hilar lymph node is not FDG avid.

False Positives FDG-PET in Lung Lesions

  • Infection: Pneumonia, mycobacterium avium complex infection, TB, fungal infection
  • Inflammation: Sarcoidosis, lipoid pneumonia, aspiration pneumonia, organizing pneumonia, amyloidosis, radiation pneumonitis
Why False Positive?
  • 18F-FDG is not specific for tumor.
  • Tissues with glucose uptake also takes FDG, especially tissues with metabolically active macrophages
  • High expression of gene such as GLUT-1 may also be a reason for high FDG uptake in inflammatory lesions

Our case - surgical resection shows organizing pneumonia in the right upper lobe.

Gilman MD, Aquino SL. State-of-the-art FDG-PET imaging of lung cancer. Semin Roentgenol 2005;40:144.

1 comment:

Know Your Images said...

Interesting post... maybe you coudl post something with other markers for PET?

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