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.