Respiratory Medicine

The common use of low-dose CT scan of thorax for screening has significantly increased the chance of detecting lung nodules. Lung nodules are defined as radiological opacities in the lungs measuring from 3 mm up to 3cm in diameter. They are classified as solid, semi-solid and ground glass nodules based on CT scan features. 

Upon detection of lung nodules, their size and nature as seen on CT scans – whether solid or ground glass – are important features for further evaluation. For patients with no risk factors for lung cancer 

• No follow-up is required if the nodules are less than 6mm in size.
• A repeat CT thorax examination is necessary 6-12 months later if the nodules are 6 to 8mm in size.
• A biopsy will be considered if the nodules are larger than 8mm. 

PET-CT is not helpful for nodules 8mm or smaller, as the glucose consumption is too low for these nodules to become positive on PET-CT scans, likely resulting in a false negative. On the other hand, PET can give false positive results as infection or inflammation will also increase glucose consumption. Given the potential for discrepancies in biopsied tissues, follow-up is required even if the biopsies test non-cancerous. 

No routine monitoring is needed for solid nodules if there are no changes in imaging after two years. However, it is advised to undergo radiological surveillance for five years for ground glass nodules due to their slow growth over time.