1. A tumor-like mass resulting from the faulty growth or development of normal cells or tissue: Harartoma is composed of one or more tissues normal to the organ but which are abnormally mixed and overgrown.

A hamartoma of the lung may contain a mixture of cartilage, connective tissue, and bronchial (windpipe in the throat) epithelium (membranous tissue covering internal organs).

Hamartomas are most frequently found in the skin which are overgrowths of blood vessels; however, they also occur in the lungs, heart, or the kidneys.

3. A tumor resulting from new growth of normal tissues: The cells of the hamartoma grow spontaneously, reach maturity, and then do not reproduce; therefore, the growth is considered to be self-limiting and benign or not harmful.

Congenital malformations that present slowly growing masses of abnormal tissues in multiple areas of the body: The multiple hamartomas are appropriate to the organ in which they are located, but they are not normally organized.

The multiple hamartomas may appear in blood vessels, and in the lung and kidney.

Multiple hamartomas are not malignant, but they cause symptoms of an illness because of the spaces they occupy.