Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at January 8, 2017

Hamartomas are tissue malformations that are not malignant like some tumors, but can cause complications when they grow in specific parts of the body.


Definition & Facts

A hamartoma is similar to a neoplasm or an abnormal yet benign growth of tissue. The tissue grows at the same rate as the tissue to which it is attached and often looks like a disorganized mass of tissue. The tissue, however, is not malignant and does not contain any cancer cells.

These neoplasms grow at a rate similar to nearby healthy tissue. They visually appear different and disorganized compared to nearby healthy tissue. They may form in different parts of the body. However, these growths do not metastasize or spread to other regions of the body like a malignant tumor. Hamartoma of the skin can appear as birthmarks.

Hamartomas may obstruct any organ in the body such as the lungs, eyes, colon, etc. There are hamartomas that are positioned in or around organs that may alter their proper function, and at times, prove to be life-threatening. They could also cause major health issues if they are found in the spleen, kidney, hypothalamus, and lips.

The most common hamartomas are found in the lungs. About 75% of benign lung tumors are hamartomas. Heart hamartomas are called cardiac rhabdomyomas which are abnormally formed cardiac muscle cells. Half of these growths lead to what is called tuberous sclerosis, which can cause congestive heart failure.

Hypothalamic hamartoma which is a hamartoma in the hypothalamus is said to be difficult to treat and can cause seizures and attacks of rage. Hamartomas that form close to the blood vessels may cause aneurysms and hemorrhage. Some studies have demonstrated a 33% chance that people with precocious puberty may have had that condition due to a hypothalamic hematoma although the relationship is still unclear.

Cowden syndrome is an inherited disorder characterized by multiple hamartomas which is associated with an increased risk of cancer. A person with Cowden syndrome has an increased risk of kidney cancer, endometrial cancer, and melanoma, among other types of cancer.

Symptoms & Complaints

The symptoms of hamartomas depend on their location. Hypothalamic hamartoma typically produces severe symptoms. Often, seizures and vision problems, bursts of laughter (gelastic seizure) and sometimes rage can be caused by a hypothalamic hamartoma.

Symptoms that manifest as early as infancy can progress into cognitive impairment and physical disability. A lung hamartoma can present additional difficulties in those who smoke cigarettes. Spleen hamartomas can cause abdominal pain.

Sometimes, the location of a hamartoma can disrupt the normal function of an organ due to its location in the body. When a hamartoma interferes with the function of a blood vessel, especially with major ones such as the renal artery, hemorrhages may occur that sometimes become life-threatening.


What causes a hamartoma depends on the type of hamartoma and is not always fully understood or known. These growths can begin developing as early as the embryonic stage. Hypothalamic hamartoma, for example, develops between 33 to 41 days into gestation.

Some hamartomas are caused by genetic factors. Patients with Cowden syndrome have a condition where there are genetic mutations in their PTEN (gene) which is a tumor suppressor gene. The malfunction of this gene leads to the multiple growth of different hamartomas in the body. These patients have an increased risk of breast cancer, thyroid cancer, and uterine cancer.

Diagnosis & Tests

Most hamartomas are not detected right away because some of them are asymptomatic, meaning they do not cause any symptoms, discomfort, or pain. Some hamartomas, particularly when found close to the surface of the skin are apparent upon a physical examination. Complete blood counts and liver function tests may also be performed.

Medical imaging examinations may be performed. X-rays, magnetic resonance imaging (MRI)s and computed tomography (CT) scans are types of imaging tests that are used in the diagnosis of hamartomas. Sometimes, with the use of standard radiology procedures, it is difficult to discern immediately the difference between hamartomas from malignancies.

Treatment & Therapy

Surgery may need to be performed. People with lung hamartomas that compress lung tissue may need to have such hamartomas removed. For people with cardiac rhabdomyomas, surgery may be necessary to prevent congestive heart failure.

Cowden syndrome patients are especially managed by a multidisciplinary team of gynecologists, surgeons and dermatologists due to its complex nature. The predisposition to different cancers such as breast cancer may lead to surgery.

Therapy may be used to suppress hormones in treating hypothalamic hematoma. Sometimes surgery is a better option only if the source if the seizure is found near the mass of the hamartoma.

Prevention & Prophylaxis

There is no known way to prevent hamartoma. There are procedures to assist in the progressive development of some hamartomas related to Cowden syndrome such as mammography to detect early on the developments that may lead to breast cancer.