Ask An Expert: Lung Spot

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Ask An Expert: Lung Spot

Question:

I have a spot on my lung that was picked up on a CAT scan of my abdomen. I am a non-smoker. What could this be besides cancer?

Answer:

Air takes up almost all of the space in your lungs, and air shows up on chest X-rays and computed tomography scans (CT or "CAT" scans) as dark patches. If you have a gray or white "spot" on your X-ray or CT scan, cancer is one possible explanation, but it is not the only one. A spot like this in the lung is also called a "solitary pulmonary nodule" or in some cases, a "coin lesion."

It is hard to estimate what fraction of lung nodules are from cancer, because most studies that estimate the frequency of cancer are looking at nodules of only one size, or looking only at nodules that have persisted over time. In one report of about 60 nodules that were 1 centimeter in size or smaller, cancer was the cause of about half of the nodules.

There are several common things that can cause nodules in the lung, other than cancer. The first is inflammation from an infection or other irritation in the lung. A fungal infection (for example, infection with the fungus Cryptococcus) can cause mild or unnoticeable symptoms. This infection can create a nodule in your lung as your immune system "walls off" the infection into a small solid capsule. Solitary pulmonary nodules can be caused by diseases that result in inflammation, such as rheumatoid arthritis or sarcoidosis. A nodule also can form during the bruising and healing that can be caused by a chest injury.

A lung nodule can be a benign growth. The most common benign growth in lungs is called a hamartoma. A hamartoma is a clump of tissue containing a variety of normal lung cells, but the cells are not organized into tubes and air sacs like a normal segment of your lung, so they can't fill with air. A second benign growth that can occur in the lung is a hemangioma, a cluster of small arteries.

Most lymph nodes in your chest are clustered next to the trachea and large blood vessels in the center of your thorax, between your two lungs. Occasionally, however, a lymph node can be away from the center, within one of your lungs. In this case, a lymph node can definitely appear on X-rays as a solitary pulmonary nodule.

Mary Pickett, M.D., is a lecturer for Harvard Medical School and an assistant professor of medicine at Oregon Health & Science University in Portland, OR. At OHSU, she practices general internal medicine and teaches medical residents and students.

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Last updated:	January 24, 2007