Lung Mass - Possible Causes and What to Expect

What Does it Mean if I Have a Lung Mass?

physician examining a chest x-ray
What is a lung mass and what are the causes?.

If your doctor has told you that you have a lung mass, it can be terrifying. What do physicians mean when they say “lung mass,” what are possible causes, does it always mean lung cancer, and what tests might be recommended to determine the cause?

Definition of a Lung Mass

A "lung mass" is defined as an abnormal spot in the lungs that is more than 3 cm (1 ½ inches) in size. If a spot (or spots) is less than 3 cm in diameter, it is called a "lung nodule." If your "mass" is 3 cm or less in diameter, check out this article on understanding lung nodules.

Possible Causes

Unfortunately, the most common cause of a mass in the lungs is one of the types of lung cancer. Lung cancer is the leading cause of cancer deaths in men and women in the United States and can occur even in people who have never smoked. In fact, the majority of people who develop lung cancer at this time do not smoke. They are either former smokers or never smoked.  At least twenty percent of women who develop lung cancer have never smoked a cigarette. That said, there are benign (non-cancerous) causes of lung masses. Some causes of a lung mass include:

  • Lung cancer.
  • Other cancers – Some cancers that may appear as a mass in the lungs include lymphomas and sarcomas.
  • Benign (non-cancerous) lung tumors – Such as hamartomas which are the most common type of benign lung tumor.
  • Metastases (spread) of cancers from other regions of the body to the lung. The most common cancers which spread to the lungs and can cause a lung mass or masses include breast cancer, colon cancer, bladder cancer, or prostate cancer.  
  • Lung abscesses.
  • AV malformations - An abnormal connection between arteries and veins that are usually present from birth.
  • Lipoid pneumonia.
  • Infections - Fungal infections such as coccidiomycosis and blastomycosis, and parasitic infections such as echinococcus (hydatid cysts).
  • Pulmonary artery aneurysms – An outpouching in the arteries that travel from the heart to the lungs can appear as a mass on imaging tests.
  • Amyloidosis - A build up of abnormal proteins that forms a mass.

What Are the Chances That My Lung Mass Is Cancer?

Sadly, the most likely diagnosis, if you have a lung mass, is lung cancer. Yet there are many non-cancerous causes, as noted above. A lung mass is more likely to be cancerous if it is described as “ground glass” on an imaging report, whereas the finding of “calcifications” is more common in benign tumors. If a tumor is described as “cavitary” it is also more likely to be benign. A history of smoking, or working in occupations with exposures to cancer-causing substances raises the chances that a tumor is cancer.

What Tests Are Done?

The first thing your doctor will want to do is perform a careful history and physical. Some of the questions she might ask include:

  • Have you ever smoked?
  • Have you traveled recently?
  • What other medical conditions do you have?
  • Do you have a family history of any medical problems including lung cancer and other lung conditions?
  • Have you been exposed to elevated radon levels in your home? Radon is the second leading cause of lung cancer.

Depending on the results of a careful history and physical exam, further tests might include:

  • A CT scan - If your doctor noted a lung mass on a chest x-ray, one of the first things she may recommend is a CT scan to look at the mass more closely. This can help define the size and location of the mass, and sometimes make sure that the mass wasn’t an “artifact” on the x-ray – that is, something that looked like a mass but wasn’t, such as an overlap of tissues.
  • MRI studies.
  • A PET Scan – A PET scan is an imaging study that looks for active growth in an area that is suspicious. For example, a suspicious area that does not light up on a PET scan may be old scar tissue whereas an area that lights up (shows sign of active growth) is more likely to be a cancerous tumor.
  • A Bronchoscopy – If the mass is in the central area of the lungs near the large airways, a bronchoscopy may be recommended. During a bronchoscopy, doctors can look for abnormalities in and near the large airways and take a biopsy if needed.
  • A fine needle biopsy – If your lung mass is in the outer regions of the lungs, your doctor may recommend a biopsy with a needle that is placed through the chest wall and into the mass to get a tissue sample.
  • Lung surgery – Sometimes it may be difficult to get a sample of the cells in your lung mass with either a needle biopsy or via a bronchoscopy. If this is the case, thoracic surgery may be recommended to get a sample of tissue.


The treatment of your lung mass will depend on upon the underlying cause. If it is a cancerous tumor of the lung or from the spread of cancer from another region of the body to the lung, treatment options may include surgery, chemotherapy, or radiation therapy. Other less common causes of lung masses, such as infections, will be treated based on the diagnosis you and your doctor determine after testing.

Benign vs Malignant Masses

It can be very confusing when you are first diagnosed with a lung nodule or lung mass. Why isn't it easier to tell if something is cancerous or not? Why are the treatments so different? The following articles can help make some of that a little clearer when it comes to understanding the difference between cancer cells and normal cells, and the differences between benign and malignant tumors.

For Those Newly Diagnosed with Lung Cancer

If your doctor is pretty sure that you lung mass is cancer, you may be feeling terrified. What does this mean? What happens next? If that describes you, take a moment to read about these first steps to take when you are diagnosed with lung cancer.


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Gould, M. et al. Evaluation of Patients With Pulmonary Nodules: When Is It Lung Cancer? ACCP Evidence-Based Clinical Practice Guidelines (2nd Edition). Chest. 2007. 132(no 3 suppl):108S-130S.

Wahidi, M. et al. Evidence for the Treatment of Patients With Pulmonary Nodules: When Is It Lung Cancer? ACCP Evidence-Based Clinical Practice Guidelines (2nd Edition). Chest. 2007. 132(no 3 suppl):94S-107S.

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