Epidermoid and Dermoid Tumor
Epidermoid and dermoid tumors, also referred to as epidermoid or dermoid cysts are slow growing benign lesions that result form an error of cell migration during embryonic development. These lesions develop when cells in the developing embryo that were destined for the skin, hair or nail tissue become entrapped in the developing brain or spinal cord. These trapped cells ultimately produce what is called an inclusion cyst and the cyst contents can vary depending on the exact cell type that was trapped. The distinction between epidermoid and dermoid cysts is that epidermoid cysts do not contain hair or sebaceous glands. Rarely these cysts can spontaneously release their contents into the brain or cerebrospinal fluid causing a form of chemical meningitis.
Epidermoid cysts are benign masses, frequently located off to the side of the brain or skull such as the cerebellopontine angle (an area along the side of the brainstem), near the pituitary gland, or within the skull. Dermoid cysts tend to me more midline in location but are relatively rare in the brain and instead occur more frequently in the spine, face or scalp. These tumors also are referred to as germ cell tumors because the original skin layer within the embryo that these trapped cells originated from is known as a germ layer.