What are benign lung tumors?

A lung tumor is the result of abnormal rates of cell division or cell death in lung tissue, or in the airways that lead to the lungs. A tumor, or abnormal buildup of tissue, may form when cells divide too quickly or do not die off as they normally should.

If the growth is 3 centimeters or less in diameter, it is commonly called a nodule. When a nodule forms in the lungs, it is called a pulmonary nodule. Any growth bigger than 3 centimeters in diameter is called a mass.

Benign lung tumors:

  • Are not cancerous, so will not spread to other parts of the body
  • Grow slowly, or might even stop growing or shrink
  • Are usually not 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

Types of benign lung tumors: hamartoma

There are a number of different kinds of benign lung tumors, the most common being hamartomas. They account for about 55% of all benign lung tumors, and 8% of all lung tumors.

Characteristics of lung hamartomas:

  • About 80% are found in the peripheral, or outer, portion of the lung's connective tissue. The remainder are found inside the bronchial tubes (the airways leading to the lungs). Deeper growths may be difficult to distinguish from cancerous nodules.
  • Are made up of "normal" tissues such as cartilage, connective tissue, fat, and muscle but in abnormal amounts.
  • Are usually less than 4 centimeters in diameter.
  • Stay within a limited area and are not likely to press against nearby tissue.
  • Usually appear in chest X-rays as a coin-like round growth.
  • May look like fluffy wool or popcorn in about 15% of cases.
  • Are found more often in males than females, and between the ages of 50 and 70.

Types of benign lung tumors: papilloma

Another type of benign lung tumor is called a papilloma. It grows in the bronchial tubes, sticking out from the surface area where it is attached. Papillomas are not very common and are divided into three types.

Categories of pulmonary papillomas:


  • Occur in both children and adults
  • May appear as just one nodule or many
  • Result from infection by human papilloma virus (HPV), the same virus that causes warts and certain sexually transmitted diseases


  • No cause has been identified
  • Are less common than squamous papillomas
  • Develop in larger airways than squamous papillomas
  • Can occur in all ages but mostly adults
  • Almost always appear as one nodule, centrally located

Mixed squamous and glandular

  • Contain a mix of squamous and glandular papilloma tissue
  • Only a small number of cases have been reported
  • Has the potential to eventually turn cancerous because the squamous cells can change over time

How common are benign lung nodules?

  • Pulmonary nodules appear in about one of every 200 chest X-rays and most 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. Pulmonary nodules are much more commonly found than are lung cancers or benign lung tumors.
  • There are few cases before the age of 35, with most cases occurring after the age of 45.

What causes benign lung nodules?

  • Healed-over "wounds" on the lung due to tuberculosis, a scar from surgery, or different types of fungal infections.
  • Infection from human papillomas virus, in some cases.
  • Smokers are at higher risk than non-smokers.
  • A cause cannot be identified in some cases.

What are the symptoms of benign lung tumors?

Often there are no symptoms that a benign lung tumor is present. More than 90% are found by accident, when a patient receives a chest X-ray or CT (computed tomography) scan for some other reason.

If symptoms do appear, they may include the following:

  • Persistent coughing or wheezing
  • Shortness of breath or difficulty breathing
  • Coughing up blood
  • Rattling sounds in the lungs
  • Higher likelihood of pneumonia
  • Lung tissue collapse


Last reviewed by a Cleveland Clinic medical professional on 04/07/2016.


  • Ganti S, et al. Giant pulmonary hamartoma. Journal of Cardiothoracic Surgery 2006, 1:19.
  • Lange S and Walsh G. Radiology of Chest Diseases, 3d ed. Stuttgart, Germany: Georg ThiemeVerlag; 2007: 151.
  • Tomashefski JF, editor. Dail and Hammar's Pulmonary Pathology: Neoplastic lung disease, 3d ed. New York, NY: Springer Science+Business Media, LLC; 2008: 534-536.

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