Q: If a 40-year-old former smoker has been told she has pulmonary (lung) nodules, does this mean lung cancer?

A: The term nodule is usually used to describe a small rounded growth or lump. This can appear anywhere on or in the body. Or it may be found on an X-ray or other type of scan. Nodules can be a sign of cancer, but more often they are benign (noncancerous) growths.

Pulmonary nodules are small rounded growths in the lung. They're usually found on chest X-rays or CT scans. Causes of pulmonary nodules include:

1. Infection of the lungs, including infections by tuberculosis, parasites or fungi that may have happened years or even decades ago

2. Exposure to certain types of lung irritants, such as coal dust or silica

3. Abnormal blood vessels (arteriovenous malformations or AVMs)

4. Minor abnormalities present since birth

5. Inflammatory conditions such as rheumatoid arthritis, sarcoidosis, or Wegener's granulomatosis

6. Lung cancer

7. Cancer that started in another organ and spread to the lung, such as metastatic breast cancer

Your doctor will perform a thorough evaluation to sort out the cause of any new nodule or nodules found. This usually starts with collecting information about you and your medical history. For example, a small lung nodule in a healthy 40-year-old person who quit smoking in their 20s is probably benign. On the other hand, several large lung nodules in a person who has or had breast cancer are very worrisome because it could mean cancer has spread.

Next, your doctor will carefully review your X-rays. Certain characteristics may make the nodules appear more or less worrisome. For example, take a smooth growth that's surrounded by calcium (which appears white on an X-ray). This is almost always left over from an old infection.

If your nodule was found on a plain X-ray, your doctor will likely order a CT scan. If you've already had a CT scan, newer types of tests such as a positron emission tomography (PET) scan may help.

If your doctor is not highly suspicious that your nodule is caused by something worrisome, he or she may simply recommend a repeat CT scan in three to six months. If the nodule remains the same size, this is usually reassuring.

But you may need to have a biopsy if you have a nodule that looks suspicious or a nodule that is growing over time. The biopsy usually can be done using a telescope. It's inserted through the mouth (bronchoscopy) or the chest wall (thoracoscopy).

(Howard LeWine, M.D., is a practicing internist at Brigham and Women's Hospital, Boston, Mass., and Chief Medical Editor of Internet Publishing at Harvard Health Publications, Harvard Medical School.)

(For additional consumer health information, please visit http://www.health.harvard.edu.)