mature teratoma
(muh-CHOOR TAYR-uh-TOH-muh)
A type of germ cell tumor that is usually made up of several different types of tissue, such as hair, muscle, and bone. Mature teratomas have cells that look almost like normal cells under a microscope. Some mature teratomas make enzymes or hormones that may cause signs and symptoms of disease. They are benign (not cancer) but may come back after being removed by surgery. Mature teratomas usually occur in the sacrum or tailbone in newborns or in the testicles or ovaries at the start of puberty. They are often called dermoid cysts.