My mother-in-law recently had a chest X-ray and was told she has a granuloma in her lung. What does that mean?

Answers from James M. Steckelberg, M.D.

A granuloma is a small area of inflammation in tissue. Granulomas are most often the result of an infection and most frequently occur in the lungs, but can occur in other parts of the body as well. Granulomas are often found incidentally on a chest X-ray done for some other reason.

The most common cause of lung granulomas in the United States is past histoplasmosis, a fungal infection that primarily affects the lungs. People who acquire pulmonary histoplasmosis that results in a lung granuloma have almost always spent some time in the Ohio River Valley or the upper Midwest. Most people with pulmonary histoplasmosis recover on their own and never suspect they have the disease because signs and symptoms are rare.

Although granulomas due to histoplasmosis are noncancerous (benign), they may resemble cancer on an X-ray, especially if they haven't calcified. Granulomas eventually become calcified and have the same density as bone, making them more clearly visible on an X-ray.

A doctor may suspect a diagnosis of granuloma by a plain chest X-ray or, if the granuloma is not apparently calcified, by computerized tomography (CT), which can detect the calcium that isn't evident on a plain chest X-ray. The images of affected tissue usually show scarring and calcification characteristic of a granuloma.

Granulomas in patients without symptoms almost never require treatment or even follow-up chest X-rays.

Oct. 10, 2015