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.

Causes

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 of 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.

Symptoms

The nodule itself rarely causes symptoms.

Exams and Tests

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.

Nodules which can be watched and likely to be benign include the following characteristics

• 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
• Repeat chest x-rays or chest CT scans are the most common way to follow the nodule. Sometimes, 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.

Biopsy of  the nodule to rule out cancer will be considered 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.

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

Outlook (Prognosis)

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.