A hamartoma is a benign, focal malformation that resembles a neoplasm in the tissue of
its origin.
This is not a malignant tumor, 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 taken for another reason.
Choristomas, forms of heterotopia, are closely related benign tumors.
These tumors also contain normal tissues but are found in abnormal locations.
Put simply, a hamartoma is an excess of normal tissue in a normal situation, and a choristoma
is an excess of tissue in an abnormal situation.
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, the colon, etc.
They are particularly likely to cause major health issues when located in the hypothalamus,
spleen or kidneys or lips.
Types Lung
The most common hamartomas occur in the lungs.
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, fat,
and connective tissue 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.
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 will often not provide definitive diagnosis, and even a CT scan may be insufficient
if the hamartoma lacks the typical 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 (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, 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 it obstructs blood flow.
Symptoms are usually from congestive heart failure; in utero 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.
Unlike most such growths, a hypothalamic hamartoma is symptomatic; it most often causes gelastic
seizures, 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.
Symptoms tend to be resistant to medical control, however 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 of the kidney was previously considered to be a hamartoma or choristoma.
Cowden syndrome Considered part of the PTEN hamartoma tumor
syndrome, which also includes Bannayan-Riley-Ruvalcaba syndrome, Proteus syndrome, and Proteus-like
syndrome Cowden syndrome is a serious genetic disorder
characterized by multiple hamartomas.
Usually skin hamartomas exist, and commonly 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.
See also Hamartia
List of cutaneous conditions References
External links eMedicine - "Lung Hamartoma"
eMedicine - "Angiomyolipoma" DermAtlas 8