| Hamartoma | |
|---|---|
 | |
| A large hamartoma of thespleen. The hamartoma is the dark circular object on the left that dominates the image. This is a cross-section; the growth is about 9 cm in diameter, while the entire spleen is about 11 cm in diameter.[1] | |
| Pronunciation |
|
| Specialty | Medical genetics,pathology  |
| Diagnostic method | Chest x-ray,CT scan,MRI,ultrasound, andbronchoscopy.[2] |
Ahamartoma is a mostly benign,[3] local malformation of cells that resembles aneoplasm 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.[4] Despite this, many hamartomas are found to have clonalchromosomal aberrations that are acquired through somatic mutations, and on this basis the termhamartoma is sometimes considered synonymous with neoplasm. Hamartomas are by definition benign, slow-growing or self-limiting,[3][4] though the underlying condition may still predispose the individual towardsmalignancies.
Hamartomas are usually caused by a genetic syndrome that affects thedevelopment cycle of all or at least multiple cells.[4] Many of these conditions are classified asovergrowth syndromes orcancer syndromes. Hamartomas occur in many different parts of the body and are most often asymptomaticincidentalomas (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 asadenomas, developmentalcysts,hemangiomas,lymphangiomas andrhabdomyomas 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 inneurofibromatosis type I andtuberous sclerosis.[5]
It is different fromchoristoma, a closely related form ofheterotopia.[6][7] The two can be differentiated as follows: a hamartoma is an excess of normal tissue in a normal situation (e.g., abirthmark on the skin), while a choristoma is an excess of tissue in an abnormal situation (e.g., pancreatic tissue in theduodenum).[8][9] The termhamartoma is from the Greek ἁμαρτία,hamartia ("error"), and was introduced by D.P.G. Albrecht in 1904.[10]
Hamartomas are caused by abnormal formation in normal tissue and can occur spontaneously or as a result of an underlying disorder. Hamartomas are most likely the result of developmental error and can manifest itself in multiple locations. The development of hamartomas has also been linked to certaingenes such asSMAD4,PTEN,STK1, andBMPR1A.[2]
Disorders associated with hamartomas includetuberous sclerosis,cowden syndrome,PTEN hamartoma tumour syndrome, andPeutz–Jeghers syndrome.[2]
About 5–8% of all solitarylung nodules and about 75% of all benign lung tumors, are hamartomas.[11] Ten percent of hamartomas are endobronchial lesions, with the majority occurring in the peripheral lungparenchyma.[12] Peripheral pulmonary hamartomas typically do not cause any symptoms.[13] Patients may experiencehemoptysis, obstructivepneumonia,dyspnea, persistentcough, andchest pain, depending on the size and location.[14] Typically, lung hamartomas appear as solitary nodules on thoraciccomputed tomography (CT) scans, with a diameter of less than 4 cm.[15]
Lung hamartomas are more common in men than in women, and may present additional difficulties in smokers.[16]
Cardiacrhabdomyomas is an uncommon, benignmesenchymal tumor that originated from striated muscle. Usually, it affects the head and neck.[17] It has been found thattuberous sclerosis is linked to 80–90% ofcardiac rhabdomyomas.[18] The symptoms may manifest aspericardial effusion,hydrops fetalis, orheart blocks.[19]
Sometimes nerves can also be affected. The most common nerve to be affected by hamartoma is reported to bemedian nerve.[20]
One of the most troublesome hamartomas occurs on thehypothalamus. Unlike most such growths, ahypothalamic hamartoma is symptomatic; it most often causesgelastic seizures, and can cause visual problems, other seizures, rage disorders associated with hypothalamic diseases, and early onset ofpuberty. 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.[21]
Renal hamartomas are benign tumors that most likely developed from birth defects in the organ. They are frequently abundant in blood vessels and contain varying amounts of fat and smooth muscle components.[22]
Amyoepithelial hamartoma, also known as apancreatic rest, isectopic pancreatic tissue found in the stomach, duodenum, or proximal jejunum. When seen onupper gastrointestinal series, 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.[23]
A hamartoma has been identified as a cause of partial outflow obstruction in theabomasum (true gastric stomach) of a dairy goat.[24]
Splenic hamartoma is an uncommon benign vascular proliferative tumor that is identified by the vascularendothelial lining cells'CD8 immunopositivity. It is made up of an unusual combination of typical splenic components, like red and white pulp.[25]
Cowden syndrome is an uncommon hereditary disorder marked by numerous hamartomas in a range of tissues from all three layers of the embryo. This is a syndrome that predisposes people tocancer and increases the risk of developing cancer in many different tissues, but particularly in the endometrium, thyroid, and breast. It is inherited autosomally dominantly, with a germ-line mutation of thePTEN tumor suppressor gene present in about 80% of patients.[26]
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.[27] They may obstruct practically any organ in the body, such as thecolon,eye, etc. They are particularly likely to cause major health issues when located in thehypothalamus,kidneys,lips, orspleen. 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.[citation needed]
| Authority control databases: National |
|---|