Lung Mass: Possible Causes and What to Expect

What Does it Mean if I Have a Lung Mass?

Diagram of a torso showing site of cancer in the lung

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, what are the chances it's lung cancer, and what tests might be recommended to determine the cause?


A "lung mass" is defined as an abnormal spot or area 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.


As noted above, the term lung nodule is used to describe smaller abnormal areas in the lungs. Overall, the chance that a lung nodule is benign is greater than the chance that it is malignant (cancerous.)

Unfortunately, the most common cause of a mass in the lungs is one of the types of lung cancer.  Before you get too upset in reading this, however, it's important to note that both the treatments for and the survival of lung cancer have improved in recent years. As you read on, keep this is mind, especially if you have known someone who had lung cancer more than a year or two ago.

Lung cancer is far too common, and is currently the leading cause of cancer deaths in men and women in the United States. Lung cancer and may occur even in people who have never smoke, and in fact, the majority (around 80 percent) of people who develop lung cancer at this time do not smoke; they are either former smokers or never smoked.

 At least 20 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:

  • 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 - Abscesses are infections which have been "walled off" and contained by the body.
  • AV malformations - An AV malformation is 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) can cause a lung mass.
  • 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 - Amyloidosis is a build up of abnormal proteins that form a mass.

Link to 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.

Questions Your Doctor Might Ask

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 pass a flexible through your mouth and down into your bronchi. This test can look for abnormalities in and near the large airways, and a biopsy can be performed 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 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? It can be helpful to learn the difference between a malignant and benign tumor.

A Word From Verywell

If your doctor is pretty sure that your lung mass is cancer, you may be feeling scared. 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. Remember that treatments are improving. Be your own advocate and learn as much as you can about your disease. There is also a wonderful lung cancer community available online with people who can provide support (the kind that only someone else living with the disease can) while helping you better understand your cancer and your options.


Kasper, DL.., Fauci AS, and Hauser, SL. Harrison's Principles of Internal Medicine. New York: Mc Graw Hill education, 2015. Print.

Pass, HI. Principles and practice of lung cancer: the official reference text of the IASLC. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins, 2010. Print.

Yao, Y., Lv, T., and Y. Song. How to Diagnose Pulmonary Nodules: From Screening to Therapy. Translational Lung Cancer Research. 2017. 6(1):3-5.