Persistent cough and spots on your lungs after a chest X-ray or CT scan may be signs of noncancerous pulmonary nodules. In some cases, though, more tests might be required to ensure the nodules are noncancerous.

A spot on the lungs usually refers to a pulmonary nodule. This is a small, round growth on the lungs that shows up as a white spot on image scans. Typically, these nodules are smaller than three 3 centimeters (cm) in diameter.

If your doctor sees a pulmonary nodule on a chest X-ray or CT scan, don’t panic. Pulmonary nodules are common, and most are benign or noncancerous.

Nodules are found on up to half of all lung CT scans. When a pulmonary nodule is cancerous, the spot or growth is usually larger than 3 cm or has other characteristics like an irregular shape.

Noncancerous pulmonary nodules can develop from conditions that cause inflammation or scar tissue on the lungs. Possible causes include:

The risk for cancer increases when:

Pulmonary nodules don’t cause symptoms. You may have a nodule on your lungs for years and never know it.

If a spot on your lungs is cancerous, you may have symptoms related to the specific type of cancer. For example, growths caused by lung cancer may cause a persistent cough or breathing difficulties.

If your doctor believes a pulmonary nodule is cancerous, they may order more tests. Diagnostic testing used to confirm or rule out cancer includes:

  • Positron emission tomography (PET) scan: These imaging tests use radioactive glucose molecules to determine if the cells that make up the nodule are dividing rapidly.
  • Biopsy: Your doctor may order a biopsy, especially if the results of the PET scan are inconclusive. During this procedure, a tissue sample is removed from the nodule. It’s then examined for cancer cells using a microscope.

Sometimes this is done by a needle biopsy that’s inserted near the edge of your lung through the chest wall. Another option is a bronchoscopy where your doctor inserts a scope through the mouth or nose and passes it through your large airways to collect cells.

A pulmonary nodule may be first detected on a chest X-ray. After that, you may need further testing to better characterize the nodule to help determine if it’s benign or cancerous.

Your doctor may request your medical history and your history of smoking. Additionally, your doctor needs to know if you’ve been exposed to secondhand smoke or environmental chemicals.

The first step of the process is examining the size and shape of the nodule. The bigger the nodule, and the more irregular the shape, the greater the risk of it being cancerous.

A CT scan can provide a clear image of the nodule and give more information about the shape, size, and location. If the results from a CT scan reveal that a nodule is small and smooth, your doctor may monitor the nodule over time to see if it changes in size or shape.

You’ll have to repeat the CT scan a few times at regular intervals. If the nodule doesn’t grow larger or change over a 2-year period, it’s unlikely to be cancer.

In addition to a CT scan, your doctor may order a tuberculin skin test or more commonly an interferon gamma release assay (IGRA) to check for latent tuberculosis.

They may also request that your blood be drawn for additional tests to rule out other causes such as local fungal infections. These may include coccidioidomycosis (commonly known as valley fever) in the southwestern states like California and Arizona or histoplasmosis in the central and eastern states, especially in areas around the Ohio and Mississippi river valleys.

If a pulmonary nodule is cancerous, your doctor will determine the best course of treatment based on the stage and type of cancer.

Treatment options can include radiation or chemotherapy to kill and prevent the spread of cancer cells. Treatment may also include surgery to remove the tumor.

In most cases, pulmonary nodules can’t be prevented. However, quitting smoking is the best way to help prevent cancerous pulmonary nodules. Early screening may help for those who are at high risk for lung cancer. If the nodules are detected early, then it’s more likely to be treated successfully. Low-dose computer tomography scans can help find these nodules before people have cancer symptoms.

In most cases, your doctor can safely say that the nodule isn’t cancer if it doesn’t increase in size or develop points, lobes, or other irregularities over a period of 2 to 5 years. At that point, if you are not at high risk for lung cancer, there’s no need for further testing.

If the nodule is cancerous, and there’s only one, it’s likely still in the early stages when treatment offers the best chance of a cure.

In some cases, a cancerous pulmonary nodule represents a metastasis from a cancer that began in another part of the body. If that’s the case, treatment will depend on the original cancer.

Other causes of lung nodules are infections, inflammatory conditions, and benign tumors or cysts. If you have any of these underlying conditions, your doctor may recommend treatment that will depend on the underlying condition.