A dermoid cyst is the growth of normal tissue in an abnormal place in the body. The cyst is benign (not cancer). It contains different types of tissue, such as hair follicles, cartilage, sweat glands, and glands that make skin oils. A dermoid cyst in the brain or spinal cord is a rare type of dermoid cyst. They often appear in children under age 10, but can also appear in older children and young adults.