Possible Causes of a Lung Mass

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 its lung cancer, and what tests might be recommended to determine the cause?

possible causes of a lung mass
Illustration by Brianna Gilmartin, Verywell


A lung mass is defined as an abnormal spot or area in the lungs that is more than 3 centimeters (cm), about 1 1/2 inches, in size. Spots smaller than 3 cm in diameter are considered lung nodules. The most common causes of a lung mass differ from that of a lung nodule, as well as the chance that the abnormality may be cancer.


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

Around 4-5% of masses found in the lungs turn out to be one of the types of lung cancer. It may be comforting to know, however, that even if a mass is lung cancer, both the treatments for and the survival have improved in recent years. Keep this in mind, especially if you have known someone who had lung cancer more than a year or two ago. In some cases, advanced lung cancer (stage 4 lung cancer) can almost be treated as a chronic disease. Immunotherapy drugs (the first approved in 2015 and now four are available) can sometimes lead to a "durable response" (oncology lingo for perhaps even a cure) for people with even the most advanced stages of the disease.

Lung cancer is far too common and is currently the leading cause of cancer deaths in men and women in the United States. Unlike the reduction of lung cancer in older men, for one group of people, lung cancer has been increasing significantly: young, never-smoking women.

Lung cancer may occur even in people who have never smoked, 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 single 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, 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 that spread and cause a mass in the lungs are breast cancer, colon cancer, bladder cancer, and prostate cancer.
  • Lung abscesses. Abscesses are infections that 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.

Chance It Is Cancer

If you have a lung mass, although the most likely diagnosis is lung cancer 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 also is more likely to be benign. A history of smoking or working in occupations with exposure 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.)
  • Are you having any symptoms such as a persistent cough, coughing up blood, shortness of breath, pain in the area of your lung, shoulder, or back, or have you had unexplained weight loss?


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. Tests like this can be especially helpful if a person has had radiation treatment for breast cancer, Hodgkin's disease, or lung cancer in the past, as radiation may cause scar tissue that looks a lot like a tumor on imaging.
  • 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 tube 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. An endobronchial ultrasound may also be done (an ultrasound that is done through the bronchi) during a bronchoscopy to better view abnormalities deeper in the lungs but relatively close to the airways.
  • 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. This may be done through small incisions and using instruments with a camera (video-assisted thoracoscopic surgery), or through a traditional incision to access the lungs (thoractomy).


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 learn about the 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.

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Article Sources

  1. Mcwilliams A, Tammemagi MC, Mayo JR, et al. Probability of cancer in pulmonary nodules detected on first screening CT. N Engl J Med. 2013;369(10):910-9. doi:10.1056/NEJMoa1214726

  2. Torre LA, Bray F, Siegel RL, Ferlay J, Lortet-tieulent J, Jemal A. Global cancer statistics, 2012. CA Cancer J Clin. 2015;65(2):87-108. doi:10.3322/caac.21262

  3. Clément-duchêne C, Vignaud JM, Stoufflet A, et al. Characteristics of never smoker lung cancer including environmental and occupational risk factors. Lung Cancer. 2010;67(2):144-50. doi:10.1016/j.lungcan.2009.04.005

Additional Reading

  • 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.