What is Hamartoma?
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 (e.g. a birthmark on the skin), and a choristoma is an excess of tissue in an abnormal situation (e.g. pancreatic tissue in the duodenum).