The two can be differentiated as follows: a hamartoma is an excess of normal tissue in a normal situation (e.g., a birthmark on the skin), while a choristoma is an excess of tissue in an abnormal situation (e.g., pancreatic tissue in the duodenum). The term hamartoma is from the Greek ἁμαρτία, hamartia ("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 and about 75% of all benign lung tumors, are hamartomas. They almost always arise from connective tissue and are generally formed of cartilage, connective tissue, and fat 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 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 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 or not 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. 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.