A solitary pulmonary nodule is a round or oval spot (lesion) in the lungs that is seen with a chest x-ray or CT scan.

More than half of all solitary pulmonary nodules are noncancerous (benign). Benign nodules have many causes, including old scars and infections.

Infectious granulomas (reactions to a past infection) cause most benign lesions. Common infections that increase the risk for developing a solitary pulmonary nodule include:

• Tuberculosis or having been exposed to TB
• Lung diseases caused by a fungus, such as:
  • Aspergillosis
  • Coccidioidomycosis
  • Cryptococcosis
  • Histoplasmosis

Lung cancer is the most common cause of cancerous (malignant) pulmonary nodules.

The nodule itself rarely causes symptoms.

A solitary pulmonary nodule is most often found on a chest x-ray or a chest CT scan, which are often done for other symptoms or reasons.

Your doctor must decide whether the nodule in your lung is probably benign (not cancer). This is more likely if:

• The nodule is small, has a smooth border, and has a solid and even appearance on an x-ray or CT scan
• You are young and do not smoke

Your doctor may then choose to just watch the nodule on x-rays.

• Repeat chest x-rays or chest CT scans are the most common way to follow the nodule. Rarely, lung PET scans may be done.
• If repeated x-rays show that the nodule size has not changed in 2 years, it is most likely benign and a biopsy is not needed.

Your doctor may choose to biopsy the nodule to rule out cancer if:

• You are a smoker
• You have other symptoms of lung cancer
• The nodule has grown in size or has changed compared to earlier x-rays

A lung needle biopsy may be done by placing a needle through the wall of your chest, or during bronchoscopy or mediastinoscopy.

Skin tests to rule out tuberculosis and other infections may also be done.

Ask your doctor about the risks of having a biopsy versus monitoring the size of the nodule with regular x-rays or CT scans. Treatment may be based on the results of the biopsy or other tests.

The outlook is usually good if the nodule is benign. If the nodule does not grow larger over a 2-year period, often nothing more needs to be done.

Gould MK, Fletcher J, Iannettoni MD, et al. Evaluation of patients with pulmonary nodules: when is it lung cancer?: ACCP evidence-based clinical practice guidelines (2nd edition). Chest. 2007;132:108S-130S.

Wahidi MM, Govert JA, Goudar RK, et al. Evidence for the treatment of patients with pulmonary nodules: when is it lung cancer?: ACCP evidence-based clinical practice guidelines (2nd edition). Chest. 2007;132:94S-107S.

Albert RH, Russell JJ. Evaluation of the solitary pulmonary nodule. Am Fam Physician. 2009;80:827-831.

Ettinger DS. Lung cancer and other pulmonary neoplasms. In: Goldman L, Ausiello D, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 197.