What are pulmonary nodules — can they cause lung cancer?

DEAR DOCTOR K:

I saw my doctor because I’ve been getting short of breath. He did an X-ray and CT scan that found three small “pulmonary nodules.” Do I have lung cancer?

DEAR READER:

There are few things more frustrating, for both you and your doctor, than when the doctor says: “Well, it’s almost surely nothing to worry about … but there is a small possibility that it’s bad.” How often does that happen? Pretty much every day, in my experience.

The tests we have available today — particularly imaging tests — are much better at spotting possible problems than the tests available when I was in medical school. But how good are they at giving you a clear answer to the simple question: “Do I have something to worry about, doctor?” Not very good at all.

Pulmonary nodules are a good example. The term nodule usually describes a small rounded growth or lump. Nodules can be a sign of cancer. But more often they are benign (noncancerous) growths.

Pulmonary nodules are found in the lung and have several possible causes. These include:

  • Lung infections, including infections that occurred years or decades ago.
  • Exposure to lung irritants, such as coal dust or silica.
  • Abnormal blood vessels.
  • Minor abnormalities that have been present since birth.
  • Inflammatory conditions.
  • Lung cancer.
  • Cancer that started in another organ and spread to the lung.

To determine what caused your nodules, your doctor will perform a thorough evaluation. This usually starts with your medical history. For example, a small lung nodule in a healthy 40-year-old who quit smoking 15 years ago is probably benign. On the other hand, several large nodules in a woman with breast cancer could mean the cancer has spread.

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

If a nodule is found on a regular X-ray, a doctor will likely order a computed tomography (CT) scan, as yours did. Newer types of tests, such as positron emission tomography (PET) scans, can provide additional information to help your doctor determine what caused your nodule. These additional tests are definitely superior to the standard X-ray in telling you there’s nothing to worry about. But they’re not perfect.

If your doctor believes your nodule is benign, he or she may recommend a repeat X-ray or scan in three to six months. At that time, your doctor will check whether the nodule has grown. If the nodule remains the same size, this is usually reassuring.

If your nodule looks suspicious or grows over time, you may need a biopsy. A small piece of the nodule will be removed and examined in a laboratory. That is the best way of knowing what you are dealing with. But it’s a procedure you have to go through, and it’s not as simple as a scan. Someday, scans will be so accurate that you won’t have to go through a biopsy.