March 24, 2009

FDG-PET and Solitary Pulmonary Nodule Assessment (2)

Fig. 1: Axial CT image shows an ill-defined 1 cm nodule in the left upper lobe with internal cavity (arrow).
Fig. 2: Axial FDG-PET image at the same level as on CT shows no uptake of the nodule. Wedge resection of the nodule reveals bronchioloalveolar carcinoma.

False negative FDG-PET for lung malignancy

  • Bronchioloalveolar carcinoma
  • Carcinoid tumor
  • Mucinous tumors
Reasons for false negativity of these tumors may be:
  • Less number of cells in tumor (low cellarity relative to tumor volume)
  • Better degree of differentiation (well-differentiated), not much nuclear atypia or less mitotic figures
  • Lower metabolic rate
  • Less peritumoral inflammation
  • Small tumor size
How to Deal?
Goes by CT appearance and clinical scenario. If there is no characteristics of benignity of the nodule, at minimum - do a closed follow up with CT.

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

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