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 a 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.
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.
Noncancerous pulmonary nodules can develop from conditions that cause inflammation or scar tissue on the lungs. Possible causes include:
- lung infections, such as mycobacterium tuberculosis
- granuloma, which are small clumps of cells that grow because of inflammation
- noninfectious diseases that cause noncancerous nodules, such as sarcoidosis and rheumatoid arthritis
- neoplasms, which are abnormal growths that can be benign or cancerous
- cancerous tumors, such as lung cancer, lymphoma, sarcoma
- metastatic tumors that spread from other parts of the body
Less than 5 percent of pulmonary nodules are malignant, or cancerous. The risk for cancer increases when:
- a nodule is large
- the nodule appears to have lobes or a pointed surface
- you are a current or former smoker
- you have a family history of lung cancer
- you've been exposed to asbestos
- you have a history of chronic obstructive lung disease
- you are over age 60
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 is benign or cancerous.
Your doctor may request information about 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 two-year period, it's unlikely to be cancer.
In addition to a CT scan, your doctor may complete a tuberculin skin test to check for tuberculosis or draw your blood to rule out other causes.
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 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 which is 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.
If a pulmonary nodule is cancerous, your doctor will determine the best course of treatment based on the stage and type of the cancer. Treatment options can include radiation or chemotherapy to kill and prevent the spread of cancer cells, or surgery to remove the tumor.
In most cases, your doctor can safely say that the nodule isn’t cancer if it doesn’t increase in size and remains small over a period of two years. At that point, there is no need for further testing.
If the nodule is cancerous and there is only one, it is likely still in the early stages when treatment offers the best chance of cure.
In some cases, a cancerous pulmonary nodule represents a metastasis from a cancer that began in another part of the body. If that is 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.