A hamartoma is a benign (noncancerous) mass that’s made of the same cells found in surrounding tissue. Most hamartomas don’t cause symptoms and aren’t serious. If a hamartoma has grown so large that it’s causing symptoms, surgery usually resolves the issue.
A hamartoma is a benign (noncancerous) growth, or mass, that contains the same types of cells located in the part of your body where the growth forms. Unlike cells in the surrounding tissue, the cells that make up a hamartoma grow in a disorganized way. These cells clump together to form an abnormal — but harmless — tumor-like mass.
Hamartoma (pronounced “HA-mar-TOH-muh”) comes from two Greek words:
Think of a hamartoma as a specific type of benign (noncancerous) tumor. A tumor is a solid mass that forms when a group of abnormal cells clumps together. Tumors can be benign or malignant (cancerous). The defining feature of a hamartoma is that the cells that clump are the same as the cells found in the surrounding normal tissue. The normal cells in a hamartoma grow together atypically.
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Hamartomas can form anywhere in your body. The most common locations include:
Hamartomas associated with certain conditions, like PTEN hamartoma tumor syndrome (PHTS), may also form in your kidneys, spleen, thyroid gland, bones or other body parts.
Hamartomas don’t spread. Unlike malignant tumors, which can spread throughout your body and damage important body structures, hamartomas stay in the place where they formed. They can cause damage if they grow so large that they impact a nearby organ or healthy tissue, but this is rare.
Several rare genetic conditions are associated with hamartomas. With these conditions, mutations (changes) in a gene can lead to hamartoma growth.
There are multiple types of hamartomas. Hamartomas include hypothalamic hamartomas, polyps (as in Peutz-Jeghers syndrome), cardiac rhabdomyomas, biliary duct hamartomas and retinal astrocytic hamartomas, among others. Hamartomas can grow anywhere in your body.
Most hamartomas are asymptomatic, which means they don’t cause symptoms. When they do cause symptoms, it’s usually because the hamartoma has grown into nearby tissue. If you do have symptoms, they’ll usually relate to the part of your body where the hamartoma has grown.
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Scientists don’t know what causes hamartomas in all instances. Genetic conditions associated with hamartomas tend to be inherited. Most involve inheriting a genetic mutation from one of your biological parents.
Your healthcare provider may recommend genetic testing or counseling if you have a syndrome that’s related to hamartomas, like PHTS.
Most hamartomas aren’t serious. Still, they can cause problems if they grow so large that they damage an organ or body structure. For example, cardiac rhabdomyomas can lead to heart problems and even heart failure if they interfere with how your heart functions. A hypothalamic hamartoma can cause hormone imbalances, cognitive dysfunction and other symptoms if it interferes with your hypothalamus’s ability to coordinate important processes in your body.
Your healthcare provider can monitor or remove a hamartoma if they’re concerned it may cause complications.
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As most hamartomas are asymptomatic, healthcare providers usually find them during imaging for an unrelated issue. Diagnosing a hamartoma can be challenging depending on where it’s located in your body because it may resemble cancerous masses.
Your provider will perform a physical exam and ask you about your medical history to help determine whether a mass is a hamartoma. Often, you’ll need additional imaging to be sure.
Diagnostic tests include:
Treatment will depend on where the mass is located and whether you’re experiencing symptoms. If it’s not causing issues, your healthcare provider may choose to monitor it instead of treating it. If it’s causing symptoms or if your provider is unable to rule out cancer, surgery is the most common treatment.
Surgeries used to remove lung hamartomas include:
Procedures used to remove hypothalamic hamartomas include:
Most hamartomas aren’t serious. If a hamartoma is impacting an organ or has grown so large that it could cause damage, surgery usually resolves the issue. In some instances, hamartomas may be difficult to remove. For example, some hypothalamic hamartomas grow close to your optic nerve. Surgery may risk damaging it. Ask your healthcare provider if your hamartoma needs to be removed. Ask about potential complications or risks if they recommend surgery or other treatments, like radiation.
Hamartomas can turn cancerous, but this is rare. Also, while hamartomas aren’t usually serious, conditions associated with hamartomas may increase your cancer risk. For example, Cowden syndrome, a type of PHTS, can cause hamartomas throughout your body. It also increases your risk of developing certain cancers. In this case, the hamartoma doesn’t increase your cancer risk. The condition does.
Your healthcare provider can advise you on whether you should be concerned about a hamartoma. Questions to ask include:
A note from Cleveland Clinic
Your healthcare provider can advise you on whether you should be concerned about a hamartoma. Usually, these growths are harmless. There’s a good chance that you won’t need treatment. On the other hand, if the hamartoma’s causing symptoms or your provider is worried about possible complications, surgery usually resolves the issue. Ask your healthcare provider about the best path forward if they discover a hamartoma.
Last reviewed on 01/25/2023.
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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy