Hamartoma
Encyclopedia
A hamartoma is a benign, focal malformation
Congenital disorder
A congenital disorder, or congenital disease, is a condition existing at birth and often before birth, or that develops during the first month of life , regardless of causation...

 that resembles a neoplasm
Neoplasia
Neoplasm is an abnormal mass of tissue as a result of neoplasia. Neoplasia is the abnormal proliferation of cells. The growth of neoplastic cells exceeds and is not coordinated with that of the normal tissues around it. The growth persists in the same excessive manner even after cessation of the...

 in the tissue of its origin. This is not a malignant
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

 tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...

, and it grows at the same rate as the surrounding tissues. It is composed of tissue elements normally found at that site, but which are growing in a disorganized mass. They occur in many different parts of the body and are most often asymptomatic and undetected unless seen on an image
Medical imaging
Medical imaging is the technique and process used to create images of the human body for clinical purposes or medical science...

 taken for another reason.

Choristomas, forms of heterotopia
Heterotopia (medicine)
In medicine, "heterotopia" refers to normal tissue present at an abnormal site or the displacement of an organ or part of an organ from its normal position. For example, gray matter heterotopia, the displacement of gray matter into the cerebral white matter or ventricles...

, are closely related benign tumors. These tumors also contain normal tissues but are found in abnormal locations.

Causes

Hamartomas result from an abnormal formation of normal tissue, although the underlying reasons for the abnormality are not fully understood. They grow along with, and at the same rate as, the organ from whose tissue they are made, and, unlike cancerous tumors, only rarely invade or compress surrounding structures significantly.

Prognosis

Hamartomas, while generally benign, can cause problems due to their location. When located on the skin, especially the face or neck, they can be extremely disfiguring, as in the case of a man with a hamartoma the size of a small orange on his eyelid. They may obstruct practically any organ in the body, such as the eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...

, the colon
Colon (anatomy)
The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...

, etc. They are particularly likely to cause major health issues when located in the hypothalamus
Hypothalamus
The Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions...

, spleen
Spleen
The spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system. In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells and holds a reserve of blood in case of hemorrhagic shock...

 or kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

s or lips
LIPS
Linguistic and Intercultural Preparation of Students for the workplace is a European Commission-funded project.It has developed pilot measures to improve students' skills and competences for their successful completion of work experiences abroad .LIPS developed an online course which is based on...

.

Lung

The most common hamartomas occur in the lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...

s. About 5-8% of all solitary lung tumors, about 75% of all benign lung tumors, are hamartomas. They almost always arise from connective tissue and are generally formed of cartilage
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...

, fat
Adipocyte
However, in some reports and textbooks, the number of fat cell increased in childhood and adolescence. The total number is constant in both obese and lean adult...

, and connective tissue
Connective tissue
"Connective tissue" is a fibrous tissue. It is one of the four traditional classes of tissues . Connective Tissue is found throughout the body.In fact the whole framework of the skeleton and the different specialized connective tissues from the crown of the head to the toes determine the form of...

 cells, although they may include many other types of cells. The great majority of them form in the connective tissue on the outside of the lungs, although about 10% form deep in the linings of the bronchii. They can be worrisome, especially if situated deep in the lung, as it is sometimes difficult to make the important distinction between a hamartoma and a lung malignancy
Lung cancer
Lung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary...

. An X-ray will often not provide definitive diagnosis, and even a CT scan
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...

 may be insufficient if the hamartoma atypically lacks cartilage and fat cells. Lung hamartomas are more common in men than in women, and may present additional difficulties in smokers. Lung hamartomas have a popcorn like appearance on chest xray.

Some lung hamartomas can compress surrounding lung tissue to a degree, but this is generally not debilitating and is often asymptomatic, especially for the more common peripheral growths. They are treated, if at all, by surgical resection, with an excellent prognosis: generally, the only real danger is the inherent possibility of surgical complications.

Heart

Cardiac rhabdomyomas are hamartomas composed of altered cardiac myocytes that contain large vacuoles and glycogen. They are the most common tumor of the heart in children and infants. There is a strong association between cardiac rhabdomyomas and tuberous sclerosis
Tuberous sclerosis
Tuberous sclerosis or tuberous sclerosis complex is a rare multi-system genetic disease that causes non-malignant tumors to grow in the brain and on other vital organs such as the kidneys, heart, eyes, lungs, and skin. A combination of symptoms may include seizures, developmental delay, behavioral...

 (characterized by hamartomas of the central nervous system, kidneys and skin, as well as pancreatic cysts; 25-50% of patients with cardiac rhabdomyomas will have tuberous sclerosis
Tuberous sclerosis
Tuberous sclerosis or tuberous sclerosis complex is a rare multi-system genetic disease that causes non-malignant tumors to grow in the brain and on other vital organs such as the kidneys, heart, eyes, lungs, and skin. A combination of symptoms may include seizures, developmental delay, behavioral...

, and up to 100% of patients with tuberous sclerosis
Tuberous sclerosis
Tuberous sclerosis or tuberous sclerosis complex is a rare multi-system genetic disease that causes non-malignant tumors to grow in the brain and on other vital organs such as the kidneys, heart, eyes, lungs, and skin. A combination of symptoms may include seizures, developmental delay, behavioral...

 will have cardiac masses by echocardiography. Symptoms depend on the size of the tumor, its location relative to the conduction system, and whether it obstructs blood flow. Symptoms are usually from congestive heart failure; in utero
In utero
In utero is a Latin term literally meaning "in the womb". In biology, the phrase describes the state of an embryo or fetus. In legal contexts, the phrase is used to refer to unborn children. Under common law, unborn children are still considered to exist for property transfer purposes.-See also:*...

heart failure may occur. If patients survive infancy, their tumors may regress spontaneously; resection in symptomatic patients has good results.

Hypothalamus

One of the most troublesome hamartomas occurs on the hypothalamus
Hypothalamus
The Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions...

. Unlike most such growths, a hypothalamic hamartoma is symptomatic; it most often causes gelastic seizure
Gelastic seizure
A gelastic seizure, also known as "gelastic epilepsy" is a rare type of seizure that involves a sudden burst of energy, usually in the form of laughing or crying. This syndrome usually occurs for no obvious reason and is uncontrollable. It is slightly more common in males than females. The term...

s, and can cause visual problems, other seizures, rage disorders associated with hypothalamic diseases, and early onset of puberty. The symptoms typically begin in early infancy and are progressive, often into general cognitive and/or functional disability. Moreover, resection is usually difficult, as the growths are generally adjacent to, or even intertwined with, the optic nerve; however, the symptoms are resistant to medical control. Luckily, surgical techniques are improving and can result in immense improvement of prognosis.

Kidneys, spleen, and other vascular organs

One general danger of hamartoma is that they may impinge into blood vessels, resulting in a risk of serious bleeding. Because hamartoma typically lacks elastic tissue, it may lead to the formation of aneurysms and thus possible hemorrhage. Where a hamartoma impinges into a major blood vessel, such as the renal artery, hemorrhage must be considered life-threatening.

Hamartomas of the spleen are uncommon, but can be dangerous. About 50% of such cases manifest abdominal pain and they are often associated with hematologic abnormalities and spontaneous rupture.

Angiomyolipoma
Angiomyolipoma
Angiomyolipoma are the most common benign tumour of the kidney and are composed of blood vessels, smooth muscle cells and fat cells. Angiomyolipoma are strongly associated with the genetic disease tuberous sclerosis, in which most individuals will have several angiomyolipoma affecting both kidneys...

 of the kidney was previously considered to be a hamartoma or choristoma, but is now known to be neoplastic.

Cowden Syndrome

  • Considered part of the PTEN hamartoma tumor syndrome (PHTS), which also includes Bannayan-Riley-Ruvalcaba syndrome, Proteus syndrome
    Proteus syndrome
    Proteus syndrome, also known as Wiedemann's syndrome , is a congenital disorder that causes skin overgrowth and atypical bone development, often accompanied by tumors over half the body....

    , and Proteus-like syndrome
  • Cowden syndrome
    Cowden syndrome
    Cowden syndrome is a rare autosomal dominant inherited disorder characterized by multiple tumor-like growths called hamartomas and an increased risk of certain forms of cancer....

    is a serious genetic disorder characterized by multiple hamartomas. Usually skin hamartomas exist, and commonly (about 66% of cases) hamartoma of the thyroid gland exists. Additional growths can form in many parts of the body, especially in mucosa, the GI tract, bones, CNS, the eyes, and the genitourinary tract. The hamartomas themselves may cause symptoms or even death, but morbidity is more often associated with increased occurrence of malignancies, usually in the breast or thyroid.

External links

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