What are benign lung tumors?

Hearing the word “tumor” naturally may cause fear. However, “tumor” simply means an abnormal buildup of tissue that occurs when cells divide too quickly or do not die off as they normally should. A lung tumor is a tumor that occurs in the lung tissue itself or in the airways that lead to the lungs. Lung tumors can be either cancerous (malignant) or benign (non-cancerous).

If you’ve been told that you have a lung tumor and it “looks like it’s benign,” what does that mean? Should you still be concerned?

Compared to malignant tumors, benign lung tumors:

  • Aren’t cancerous, so won’t spread to other parts of the body.
  • Grow slowly, or might even stop growing or shrink.
  • Aren’t usually life-threatening.
  • Usually do not need to be removed.
  • Can expand and push against nearby tissues but will not invade, destroy, or replace other tissues.

Are there different types of benign lung tumors?

Yes, there are several types of benign lung tumors. Tumors that are generally larger than three centimeters (1.2 inches) are called masses. If your tumor is three centimeters or less in diameter, it’s commonly called a nodule. If the nodule forms in your lungs, it’s called a pulmonary nodule.

Types of benign lung tumors and nodules include:


Hamartomas are the most common type of benign lung nodule. They account for about 55% of all benign lung tumors, and 8% of all lung tumors. About 80% are found in the outer portion of the lung's connective tissue. The rest are found inside the bronchial tubes (the airways leading to the lungs).

Hamartomas are made up of "normal" tissues such as cartilage, connective tissue, fat, and muscle but in abnormal amounts. They are usually less than four centimeters in diameter and appear in chest X-rays as a coin-like round growth. In about 15% of cases they may look like fluffy wool or popcorn. Hamartomas usually stay within a limited area and are not likely to press against nearby tissue. They are found more often in males than females, and between the ages of 50 and 70.

Bronchial adenomas

Adenomas are another common type of benign lung nodule. They grow in the large airways of the lungs (bronchi) and in the mucus glans or ducts of the windpipe.


Papillomas are a less common type of benign lung tumor. They grow in the bronchial tubes, sticking out from the surface area where they attached. Papillomas are divided into three types.

  • Squamous: One or more squamous papillomas can occur in both children and adults. They result from infection by the human papilloma virus (HPV), the same virus that causes warts and certain sexually transmitted diseases.
  • Glandular: These papillomas are less common than squamous papillomas and develop in larger airways compared with squamous papillomas. They occur in all ages but mostly adults. They almost always appear as one nodule, centrally located. No cause has been identified.
  • Mixed squamous and glandular: These papillomas contain a mix of squamous and glandular papilloma tissue. Only a small number of cases have been reported. These papillomas have the potential to eventually turn cancerous because the squamous cells can change over time.

Other benign lung tumors

Other rare tumors include chondromas, fibromas, neurofibromas and lipomas. These tumors are made up of connective tissue or fatty tissue.

How common are benign lung nodules?

Pulmonary nodules are fairly common. They are seen in about one of every 500 chest X-rays and in about one out of every 100 chest CT scans. At least 60% of pulmonary nodules seen on chest X-rays turn out to be benign, and 99% of those on chest CT are benign. About half the people who smoke and are over age 50 will have nodules on a CT scan of their chest.

What causes benign lung nodules?

There are many possible causes of benign lung tumors and nodules. These include:

  • Granulomas (small clumps of inflamed cells) that develop as a result of a bacterial infection such as tuberculosis or from fungal infections such as histoplasmosis or coccidiomycosis.
  • A lung abscess (pus-filled infection usually caused by bacteria).
  • Inflammation from such diseases as rheumatoid arthritis, sarcoidosis or Wegener’s granulomatosis.
  • Infection from human papilloma virus.
  • Birth defects such as a lung cyst, scars, or other lung malformation.
  • No known cause.

What are the symptoms of benign lung tumors?

You may not have any symptoms. More than 90% of nodules are found by accident, when you get a chest X-ray or CT (computed tomography) scan for some other reason.

If you do have symptoms, they may include:

  • Mild cough that lasts for a long time.
  • Shortness of breath, difficulty breathing, wheezing.
  • Coughing up blood.
  • Rattling sounds in the lungs.

Last reviewed by a Cleveland Clinic medical professional on 07/15/2020.


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