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A hamartoma is a mostly benign, local malformation of cells that resembles a
neoplasm A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...
of local tissue but is usually due to an overgrowth of multiple aberrant cells, with a basis in a systemic genetic condition, rather than a growth descended from a single mutated cell ( monoclonality), as would typically define a benign neoplasm/tumor. Despite this, many hamartomas are found to have clonal
chromosomal aberrations A chromosomal abnormality, chromosomal anomaly, chromosomal aberration, chromosomal mutation, or chromosomal disorder, is a missing, extra, or irregular portion of chromosomal DNA. These can occur in the form of numerical abnormalities, where ther ...
that are acquired through somatic mutations, and on this basis the term ''hamartoma'' is sometimes considered synonymous with neoplasm. Hamartomas are by definition benign, slow-growing or self-limiting, though the underlying condition may still predispose the individual towards
malignancies Malignancy () is the tendency of a medical condition to become progressively worse. Malignancy is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous ''benign'' tumor in that a malignancy is not s ...
. Hamartomas are usually caused by a genetic syndrome that affects the
development cycle In software engineering, a software development process is a process of dividing software development work into smaller, parallel, or sequential steps or sub-processes to improve design, product management. It is also known as a software devel ...
of all or at least multiple cells. Many of these conditions are classified as
overgrowth syndromes Overgrowth syndromes in children constitute a group of rare disorders that are characterised by tissue hypertrophy. Individual overgrowth syndromes have been shown to overlap with regard to clinical and radiologic features. The details of the gene ...
or
cancer syndromes A cancer syndrome, or family cancer syndrome, is a genetic disorder in which inherited genetic mutations in one or more genes predispose the affected individuals to the development of cancers and may also cause the early onset of these cancers. Ca ...
. Hamartomas occur in many different parts of the body and are most often asymptomatic
incidentaloma In medical or research imaging, an incidental imaging finding (also called an incidentaloma) is an unanticipated finding which is not related to the original diagnostic inquiry. As with other types of incidental medical findings, they may represe ...
s (undetected until they are found incidentally on an imaging study obtained for another reason). Additionally, the definition of hamartoma versus benign neoplasm is often unclear, since both lesions can be clonal. Lesions such as
adenoma An adenoma is a benign tumor of epithelial tissue with glandular origin, glandular characteristics, or both. Adenomas can grow from many glandular organs, including the adrenal glands, pituitary gland, thyroid, prostate, and others. Some adenom ...
s, developmental
cyst A cyst is a closed sac, having a distinct envelope and cell division, division compared with the nearby Biological tissue, tissue. Hence, it is a cluster of Cell (biology), cells that have grouped together to form a sac (like the manner in which ...
s,
hemangioma A hemangioma or haemangioma is a usually benign vascular tumor derived from blood vessel cell types. The most common form, seen in infants, is an infantile hemangioma, known colloquially as a "strawberry mark", most commonly presenting on the ski ...
s,
lymphangioma Lymphangiomas are malformations of the lymphatic system characterized by lesions that are thin-walled cysts; these cysts can be macroscopic, as in a cystic hygroma, or microscopic. The lymphatic system is the network of vessels responsible for ...
s and
rhabdomyoma A rhabdomyoma is a benign tumor of striated muscle. Rhabdomyomas may be either "cardiac" or "extra cardiac" (occurring outside the heart). Extracardiac forms of rhabdomyoma are sub classified into three distinct types: adult type, fetal type, and ...
s within the kidneys, lungs or pancreas are interpreted by some experts as hamartomas while others consider them true neoplasms. Moreover, even though hamartomas show a benign histology, there is a risk of some rare but life-threatening complications such as those found in neurofibromatosis type I and
tuberous sclerosis Tuberous sclerosis complex (TSC) is a rare multisystem autosomal dominant genetic disease that causes non-cancerous tumours to grow in the brain and on other vital organs such as the kidneys, heart, liver, eyes, lungs and skin. A combination ...
. It is different from
choristoma Choristomas, a form of heterotopia, are masses of normal tissues found in abnormal locations. In contrast to a neoplasm or tumor, the growth of a choristoma is normally regulated. It is different from a hamartoma. The two can be differentiated a ...
, a closely related form of heterotopia. The two can be differentiated as follows: a hamartoma is an excess of normal tissue in a normal situation (e.g., a
birthmark A birthmark is a congenital, benign irregularity on the skin which is present at birth or appears shortly after birth—usually in the first month. They can occur anywhere on the skin. Birthmarks are caused by overgrowth of blood vessels, melanocy ...
on the skin), while a choristoma is an excess of tissue in an abnormal situation (e.g., pancreatic tissue in the
duodenum The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine m ...
). The term ''hamartoma'' is from the Greek ἁμαρτία, ''
hamartia The term ''hamartia'' derives from the Greek , from ''hamartánein'', which means "to miss the mark" or "to err". It is most often associated with Greek tragedy, although it is also used in Christian theology. The term is often said to depic ...
'' ("error"), and was introduced by D.P.G. Albrecht in 1904.


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.


Diagnosis


Types


Lung

About 5–8% of all solitary
lung nodules A lung nodule or pulmonary nodule is a relatively small focal density in the lung. A solitary pulmonary nodule (SPN) or coin lesion, is a mass in the lung smaller than three centimeters in diameter. A pulmonary micronodule has a diameter of less th ...
and about 75% of all benign lung tumors, are hamartomas. They almost always arise from connective tissue and are generally formed of
cartilage Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck an ...
,
connective tissue Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tiss ...
, and
fat In nutrition science, nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such chemical compound, compounds, most commonly those that occur in living beings or in food. The term often refers spec ...
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
bronchi A bronchus is a passage or airway in the lower respiratory tract that conducts air into the lungs. The first or primary bronchi pronounced (BRAN-KAI) to branch from the trachea at the carina are the right main bronchus and the left main bronchus. ...
. 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. An
X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10  picometers to 10  nanometers, corresponding to frequencies in the range 30&nb ...
will often not provide a definitive diagnosis, and even a CT scan may be insufficient if the hamartoma lacks the typical cartilage and fat cells. Lung hamartomas may have popcorn-like calcifications on chest xray or computed tomography (CT scan). Lung hamartomas are more common in men than in women, and may present additional difficulties in smokers. 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
rhabdomyoma A rhabdomyoma is a benign tumor of striated muscle. Rhabdomyomas may be either "cardiac" or "extra cardiac" (occurring outside the heart). Extracardiac forms of rhabdomyoma are sub classified into three distinct types: adult type, fetal type, and ...
s are hamartomas composed of altered cardiac
myocyte A muscle cell is also known as a myocyte when referring to either a cardiac muscle cell (cardiomyocyte), or a smooth muscle cell as these are both small cells. A skeletal muscle cell is long and threadlike with many nuclei and is called a muscl ...
s that contain large
vacuole A vacuole () is a membrane-bound organelle which is present in plant and fungal cells and some protist, animal, and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic mo ...
s and
glycogen Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in animals, fungi, and bacteria. The polysaccharide structure represents the main storage form of glucose in the body. Glycogen functions as one o ...
. They are the most common tumor of the heart in children and infants. There is a strong association between cardiac
rhabdomyomas A rhabdomyoma is a benign tumor of striated muscle. Rhabdomyomas may be either "cardiac" or "extra cardiac" (occurring outside the heart). Extracardiac forms of rhabdomyoma are sub classified into three distinct types: adult type, fetal type, and g ...
and
tuberous sclerosis Tuberous sclerosis complex (TSC) is a rare multisystem autosomal dominant genetic disease that causes non-cancerous tumours to grow in the brain and on other vital organs such as the kidneys, heart, liver, eyes, lungs and skin. A combination ...
(characterized by hamartomas of the
central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all par ...
, kidneys, and skin, as well as pancreatic cysts); 25-50% of patients with cardiac rhabdomyomas will have tuberous sclerosis, and up to 100% of patients with tuberous sclerosis will have cardiac masses by echocardiography. Symptoms depend on the size of the tumor, its location relative to the conduction system, and whether or not it obstructs blood flow. Symptoms are usually from
congestive heart failure Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome, a group of signs and symptoms caused by an impairment of the heart's blood pumping function. Symptoms typically include shortness of breath, excessive fatigue, a ...
; ''
in utero ''In Utero'' is the third and final studio album by American rock band Nirvana. It was released on September 21, 1993, by DGC Records. After breaking into the mainstream with their second album, ''Nevermind'' (1991), Nirvana hired Steve Albin ...
'' heart failure may occur. If patients survive infancy, their tumors may regress spontaneously; resection in symptomatic patients has good results. Nerves Sometimes nerves can also be affected. The most common nerve to be affected by hamartoma is reported to be median nerve.


Hypothalamus

One of the most troublesome hamartomas occurs on the
hypothalamus The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamu ...
. Unlike most such growths, a
hypothalamic hamartoma Tuber cinereum hamartoma is a benign tumor in which a disorganized collection of neurons and glia accumulate at the tuber cinereum of the hypothalamus on the floor of the third ventricle. It is a congenital malformation, included on the spectru ...
is symptomatic; it most often causes
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. This syndrome usually occurs for no obvious reason and is uncontrollable. It is slightly more ...
s, and can cause visual problems, other seizures, rage disorders associated with hypothalamic diseases, and early onset of
puberty Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a girl, the testes in a boy. ...
. 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. Symptoms tend to be resistant to medical control; however, surgical techniques are improving and can result in immense improvement of prognosis.


Kidneys, stomach, spleen and other vascular organs

One general danger of hamartomas is that they may impinge into blood vessels, resulting in a risk of serious bleeding. Because a hamartoma typically lacks elastic tissue, it may lead to the formation of
aneurysm An aneurysm is an outward bulging, likened to a bubble or balloon, caused by a localized, abnormal, weak spot on a blood vessel wall. Aneurysms may be a result of a hereditary condition or an acquired disease. Aneurysms can also be a nidus (s ...
s and thus possible
hemorrhage Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, vag ...
. Where a hamartoma impinges into a major blood vessel, such as the
renal artery The renal arteries are paired arteries that supply the kidneys with blood. Each is directed across the crus of the diaphragm, so as to form nearly a right angle. The renal arteries carry a large portion of total blood flow to the kidneys. Up to a ...
, hemorrhage must be considered life-threatening.
Angiomyolipoma Angiomyolipomas are the most common benign tumour of the kidney. Although regarded as benign, angiomyolipomas may grow such that kidney function is impaired or the blood vessels may dilate and burst, leading to bleeding. Angiomyolipomas are st ...
of the kidney was previously considered to be a hamartoma or
choristoma Choristomas, a form of heterotopia, are masses of normal tissues found in abnormal locations. In contrast to a neoplasm or tumor, the growth of a choristoma is normally regulated. It is different from a hamartoma. The two can be differentiated a ...
. A myoepithelial hamartoma, also known as a pancreatic rest, is ectopic pancreatic tissue found in the stomach, duodenum, or proximal jejunum. When seen on
upper gastrointestinal series An upper gastrointestinal series, also called a barium swallow, barium study, or barium meal, is a series of radiographs used to examine the gastrointestinal tract for abnormalities. A contrast medium, usually a radiocontrast agent such as barium ...
, a pancreatic rest may appear to be a submucosal mass or gastric neoplasm. Most are asymptomatic, but they can cause dyspepsia or upper gastrointestinal bleeding. A hamartoma has been identified as a cause of partial outflow obstruction in the abomasum (true gastric stomach) of a dairy goat. 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.


Cowden syndrome

Cowden syndrome Cowden syndrome (also known as Cowden's disease and multiple hamartoma syndrome) is an autosomal dominant inherited condition characterized by benign overgrowths called hamartomas as well as an increased lifetime risk of breast, thyroid, uterine, ...
is a serious genetic disorder characterized by multiple hamartomas. Usually skin hamartomas exist, and commonly (in about 66% of cases) hamartoma of the
thyroid gland The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobe (anatomy), lobes. The lower two thirds of the lobes are connected by a thin band of Connective tissue, tissue cal ...
exists. Additional growths can form in many parts of the body, especially in bones, CNS, the eyes, the genitourinary tract, the
GI tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans ...
, and
mucosa A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...
. 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. Cowden syndrome is considered a
PTEN hamartoma tumor syndrome Multiple hamartoma syndrome is a syndrome characterized by more than one hamartoma. It is sometimes equated with Cowden syndrome. However, MeSH also includes Bannayan–Zonana syndrome (that is, Bannayan–Riley–Ruvalcaba syndrome) and Lhermit ...
(PHTS), which also includes Bannayan–Riley–Ruvalcaba syndrome,
Proteus syndrome Proteus syndrome is a rare disorder with a genetic background that can cause tissue overgrowth involving all three embryonic lineages. Patients with Proteus syndrome tend to have an increased risk of embryonic tumor development.Freedberg, et al. ...
and
Proteus-like syndrome Proteus-like syndrome (PLS) is a condition similar to Proteus syndrome, but with an uncertain cause.It's characterized by skeletal and hamartous overgrowth of multiple tissues, nevi in cerebriform connective tissue, blood vessel malformations and l ...
.


Prognosis

Hamartomas, while generally benign, can cause problems due to their location. For example, when located on the skin, especially on the face or neck, they can be very disfiguring. Cases have been reported of hamartomas the size of a small orange. They may obstruct practically any organ in the body, such as the colon, eye, etc. They are particularly likely to cause major health issues when located in the
hypothalamus The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamu ...
,
kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blood ...
s,
lips The lips are the visible body part at the mouth of many animals, including humans. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech. Human lips are a tactile sensory organ, and can be ...
, or
spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .
. They can be removed surgically if necessary, and are not likely to recur. Prognosis will depend upon the location and size of the lesion, as well as the overall health of the patient.


See also

*
Hamartia (medical term) A hamartia is a focal malformation consisting of disorganized arrangement of tissue types that are normally present in the anatomical area. A hamartia is not considered to be a tumor, and is distinct from a hamartoma, which describes a benign neopl ...
*
List of cutaneous conditions Many skin conditions affect the human integumentary system—the organ system covering the entire surface of the body and composed of skin, hair, nails, and related muscle and glands. The major function of this system is as a barrier against t ...


References


External links

* * {{Authority control Dermal and subcutaneous growths Anatomical pathology