What Are Hamartomas?

A Type of Non-Cancerous Tumor

A hamartoma is a benign tumor that may occur in the lungs, heart, skin, brain, breast, or other regions. They are made up of abnormal but not cancerous cells similar to the cells that make up the tissue where they originate.

Hamartomas can look similar to cancer on imaging studies, and for this reason, can be very frightening. In some regions of the body, they may not cause any symptoms. They can sometimes shrink on their own, but in other cases, they can cause complications.

They may also occur as part of syndromes that predispose people to cancer in several different organs. Often, there are no symptoms associated with a hamartoma, and they are found incidentally when a test is ordered for another reason, but when they cause symptoms, it is often related to the location where they occur.

Pulmonary hamartoma
Nephron / Wikimedia Commons / CC BY 3.0

Hamartoma vs. Healthy Tissue

A hamartoma is a benign (non-cancerous) tumor that is made up of “normal” tissues that are found in the region in which they grow. For example, a lung (pulmonary) hamartoma is a growth of non-cancerous tissues including fat, connective tissue, and cartilage that is found in the regions of the lungs.

The difference between hamartomas and normal tissue is that hamartomas grow in a disorganized mass. Most hamartomas grow slowly, at a rate similar to normal tissues. They are more common in men than in women. While some are hereditary, nobody knows for sure what causes many of these growths to occur.

Hamartoma Symptoms

Hamartomas may not cause any symptoms, or they may cause discomfort due to pressure on nearby organs and tissues. These symptoms vary depending upon the location of the hamartoma.

One of the most common "symptoms" is fear, as these tumors can look very much like cancer when found, especially on imaging tests.

Common Hamartoma Locations

Hamartomas can occur almost anywhere in the body. Some of the more common areas include:

  • Lungs: This is the most common location. If hamartomas obstruct an airway, it can lead to pneumonia and bronchiectasis.
  • Skin: The tumors can appear anywhere on the skin but are especially common on the face, lips, and neck.
  • Heart: Hamartomas are the most common heart tumor in children. They can cause symptoms of heart failure.
  • Hypothalamus: Symptoms from pressure on nearby brain structures is relatively common and can include seizures, personality changes, and early puberty onset.
  • Kidneys: The tumors occasionally cause kidney dysfunction.
  • Spleen: A hamartoma in this organ may cause abdominal pain.
  • Breast: The tumors account for about 5% of benign breast lumps.

Lung (Pulmonary) Hamartomas

Hamartomas are the third most common cause of solitary pulmonary nodules in the lung. They're often discovered accidentally when chest imaging is done for some other reason.

With the increased use of CT screening for lung cancer in people at risk, it’s likely that more people will be diagnosed with hamartomas in the future.

If you have recently had CT screening and your healthcare provider is considering that you may have a benign tumor such as a hamartoma, ask about what happens when you have a nodule on screening and the chances that it's cancer.

Hamartomas can be difficult to distinguish from cancers but do have some characteristics that set them apart. A description of “popcorn calcification"—meaning images that look like popcorn on a CT scan—is almost diagnostic.

Calcifications (deposits of calcium that appear white on X-ray studies) are common. Cavitation, a central area of tissue breakdown seen on X-rays, is uncommon. Most of these tumors are less than 4 centimeters (2 inches) in diameter.

In addition to hamartomas, there are several other types of benign lung nodules.

Can Hamartomas Spread?

Unlike malignant (cancerous) tumors, hamartomas do not usually spread to other regions of the body. That said, depending on their location, they can cause damage by placing pressure on nearby structures.

It’s also important to note that people with Cowden’s disease (a syndrome in which people have multiple hamartomas) are more likely to develop cancers, especially of the breast and thyroid. So even though hamartomas are benign, your healthcare provider may want to do a thorough examination and possibly imaging studies to rule out the presence of cancer.

What Causes Hamartomas?

Nobody is sure what causes hamartomas, although they are more common in people with some genetic syndromes such as Cowden's disease.

Hamartomas and Cowden Syndrome

Hamartomas often occur as part of the hereditary syndrome known as Cowden’s disease. An autosomal dominant genetic mutation most often causes Cowden's disease, meaning that if either your father or mother inherits the mutation, the chance that you will have it as well is around 50%.

In addition to multiple hamartomas (related to a form of PTEN gene mutation,) people with this syndrome often develop cancers of the breast, thyroid, and uterus, often beginning in their 30s and 40s.

Syndromes such as Cowden's syndrome help explain why your healthcare provider should have a thorough history of any cancers (or other conditions) which run in your family. In syndromes such as these, not all people will have one type of cancer, but a combination of certain types of cancer is likely.

Diagnosis and Treatment

The diagnosis of a hamartoma will depend on where it occurs. Since they can appear similar to a malignant tumor (cancer) on imaging, a biopsy is often needed to confirm the diagnosis.

Treatment options for a hamartoma will depend largely on the location of the tumor and whether or not it is causing symptoms. If hamartomas are not causing symptoms, your healthcare provider may recommend that the tumor be left alone and observed over time.


There has been much discussion over whether hamartomas should be observed or removed surgically. A 2015 review of studies attempted to clarify this issue by weighing the risk of mortality and complications due to surgery with the risk of recurrence of the tumor.

The conclusion is that a diagnosis can usually be made by a combination of imaging studies and fine needle biopsy and that surgery should be reserved for people who have symptoms due to their tumor or for people in whom there is still some doubt about the diagnosis.

Procedures, when needed for pulmonary hamartomas include wedge resection (removal of the tumor and a wedge-shaped section of tissue surrounding the tumor), lobectomy (removal of one of the lobes of a lung), or pneumonectomy (removal of a lung).

Questions to Ask Your Healthcare Provider

If you've been diagnosed with a hamartoma, make sure you understand your diagnosis and whether treatment is needed. Start with these questions:

  • Will your hamartoma need to be removed (for example, will it cause any problems if left in place)?
  • What symptoms might you expect if it grows?
  • What type of procedure does your healthcare provider recommend to remove your tumor?
  • Will you need any special follow-up care in the future?
  • Could a genetic mutation have caused your tumor? If so, should you have any special follow-up care (e.g., more frequent mammograms)?
  • Would your healthcare provider recommend genetic counseling?

If you're considering genetic testing for cancer, it's helpful to have genetic counseling first.

A Word From Verywell

Hamartomas are benign (noncancerous) tumors that will not spread to other parts of your body. Sometimes they are left alone, but if they are causing symptoms due to their location, or if the diagnosis is uncertain, surgery to remove the tumor may be recommended.

For some people, a hamartoma may be a sign of a gene mutation that can increase the risk of some cancers such as breast cancer and thyroid cancer. It's important to talk to your healthcare provider about any specialized testing you should have if this is the case. Talking with a genetic counselor may also be recommended.

Frequently Asked Questions

  • Should hamartomas be removed?

    Yes, if they're causing symptoms or your healthcare provider isn't 100% sure it's a benign tumor. Otherwise, they can be left alone.

  • How do you treat hamartoma?

    Hamartomas can be surgically removed if they're causing problems. While you await surgery, you may feel better if your symptoms are treated. (This varies depending on the location and symptoms.) Otherwise, no treatment is generally needed.

  • Do hamartomas become malignant?

    Rarely, hamartomas can become malignant (cancerous).

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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.
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Additional Reading

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."