Possible Causes of a Lung Mass

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If your healthcare provider has told you that you have a lung mass, you might be worried. However, a lung mass has several possible causes, including health issues—such as treatable infections or lung cancer. You will likely need further testing to identify the exact nature of your lung mass, and treatment can help resolve the cause.

possible causes of a lung mass

Verywell / Brianna Gilmartin


A lung mass is defined as an abnormal spot or area in the lungs larger than 3 centimeters (cm), about 1.5 inches, in size. Spots smaller than 3 cm in diameter are considered lung nodules.


The most common causes of a lung mass differ from those of a lung nodule. The chance that the abnormality may be malignant (cancerous) is lower for a lung nodule than it is for a mass.


Around 4-5% of masses found in the lungs turn out to be lung cancer. Diagnostic tests would determine the type of lung cancer.

Lung cancer treatments have advanced in recent years, as has survival. 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 currently the leading cause of cancer deaths in men and women in the United States. The incidence has been declining among older men, but it has been increasing among 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.

Cancers other than lung cancer may also appear as a mass in the lungs. These include lymphomas and sarcomas.

Metastases (spread) of cancers from other regions of the body to the lung is another cause. The most common cancers that spread to the lungs are breast cancer, colon cancer, and bladder cancer.

Benign Causes

Sometimes lung masses have noncancerous causes. These benign causes are not cancer, and they will not metastasize, but some can cause serious health complications and may need to be monitored over time and/or treated.

Some benign causes of a lung mass include:

  • Benign (noncancerous) lung tumors: Such as hamartomas, the most common type of benign lung tumor
  • Lung abscesses: Infections that have been "walled off" and contained by the body
  • AV malformations: Abnormal connection between arteries and veins that are usually present from birth
  • Lipoid pneumonia
  • Fungal infections: Such as coccidiomycosis and blastomycosis
  • 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 form a mass


Your healthcare provider will take a careful history and do a physical examination as part of the assessment of your lung mass.

Some of the questions your healthcare provider 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, lung pain, shoulder pain, or back pain, or have you had unexplained weight loss?

Depending on the results of your history and physical exam, further tests might include imaging and/or a biopsy.


If your healthcare provider noted a lung mass on your chest X-ray, they may recommend that you have computerized tomography (CT) or magnetic resonance imaging (MRI) scan to look at the mass more closely.

These tests could 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.

A positron emission tomography (PET) scan is an imaging study that detects increased metabolic activity associated with active growth. 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 signs of increased metabolism) is more likely to be a cancerous tumor.

These tests 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 resembles a tumor on X-ray.


If the mass is in the central area of the lungs near the large airways, a bronchoscopy may be recommended. During a bronchoscopy, healthcare providers 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 that are deep in the lungs and relatively close to the airways.

Fine Needle Biopsy

If your lung mass is in the outer regions of the lungs, your healthcare provider may recommend a fine needle 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).

Benign vs. Malignant Masses

The imaging and biopsy are done to provide information about the size, appearance, location, and cells in the mass.

Chance It Is Cancer

If you have a lung mass, the most likely diagnosis is lung cancer. But there are many noncancerous causes.

  • A lung mass is more likely to be cancerous if it is described as “ground glass” on an imaging report
  • The finding of “calcifications” is more common in benign tumors
  • If a tumor is described as “cavitary” it 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


The treatment of your lung mass will depend on the underlying cause. If it is a primary cancerous tumor of the lung or metastatic 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 your healthcare provider determines after testing.

Frequently Asked Questions

  • What is a benign lung mass?

    A benign mass is an abnormal cluster of tissue that develops in the lung but is not cancerous. That means it won’t spread to other parts of the lung or beyond and is unlikely to be dangerous or life threatening. Often, benign masses or tumors don’t need to be removed.

  • What usually causes benign lung tumors?

    The most common type of benign lung tumors are hamartomas. Healthcare providers don’t fully understand what causes these growths, but there seems to be a genetic link. People with an inherited disease known as Cowden syndrome have a greater risk for these growths.

  • How can a healthcare provider tell if a mass is cancerous or benign?

    Based on an imaging test, healthcare providers will look for common aspects of a cancerous tumor. These are often larger and can appear in different parts of the lung than benign growths. Healthcare providers will then order additional tests such as a needle biopsy or bronchoscopy to take a tissue sample.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  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

  4. Cleveland Clinic. Benign lung tumors. Updated July 15, 2020.

  5. Gammon A, Jasperson K, Champine M. Genetic basis of Cowden syndrome and its implications for clinical practice and risk management. Appl Clin Genet. 2016;9:83–92. Published 2016 Jul 13. doi:10.2147/TACG.S41947

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.

By Lynne Eldridge, MD
 Lynne Eldrige, MD, is a lung cancer physician, patient advocate, and award-winning author of "Avoiding Cancer One Day at a Time."