A solitary pulmonary nodule (SPN) is an abnormal growth in the lung. Often a person who has an SPN does not have any respiratory symptoms. A chest X-ray or CT scan done for some other reason usually detects an SPN.
An SPN found on a chest X-ray does not mean lung cancer is present. A past lung infection can cause a noncancerous SPN. Only about half of SPNs are cancer. Noncancerous SPNs often are caused by a previous infection in the lung. Further tests can be done to find out whether the SPN is noncancerous (benign) or cancerous (malignant).
A CT scan normally is done to help find out the growth rate, the shape of the nodule, and the pattern of calcification in the nodule to help identify whether it is cancerous. Positron emission tomography (PET) scans are being studied to find out whether they can help distinguish between noncancerous and cancerous SPNs.
In general, the larger the SPN, the more likely it is to be cancerous. Your doctor may use a probability of cancer (PCA) table to help figure out the risk that an SPN is cancerous. Then he or she may recommend follow-up testing with a biopsy or regular CT scans or, if it is very likely the SPN is cancerous, the doctor may suggest finding out its stage and removing it with surgery.
The following table shows when solitary pulmonary nodule is likely or not likely to be cancer. None of these are true in every case, but these factors are used to help decide whether further testing or treatment is needed.1
Solitary pulmonary nodule: Is it likely to be cancer?
| It's probably not cancer|| It's probably cancer|
- You are younger than 30.
- The nodule is small: 2 mm (0.08 in.) to5 mm (0.2 in.).
- The nodule has a smooth, well-defined edge.
- You have never smoked.
- The nodule has thick areas (dense calcifications).
- The nodule has not changed size for more than 2 years.
- You are older than 30.
- The nodule is large: 6 mm (0.25 in.) to 45 mm (1.8 in.).
- The nodule has edges that are poorly-defined, or a CT scan shows a halo.
- You are a smoker. The more you have smoked, the more likely the SPN is to be cancer.
- The nodule has sparse calcifications.
- The nodule is growing steadily or rapidly.