Congenital dermoid cyst of the middle ear.

Dermoid cysts of the head and neck are rare lesions comprised of epidermal and mesodermal elements. We report a dermoid cyst presenting in the middle ear of the youngest patient reported to date. Structures of endodermal descent were also identified, but, given that the entire middle ear mucosa is of endodermal origin, specific classification as a teratoma would be imprecise. This lesion is interesting in that it did not directly involve the mastoid. Possible embryologic sites of origin are discussed.