Neonatal dermoid cyst of the floor of the mouth extending to the midline neck.

We describe a male neonate who presented at birth with a compressible dermoid cyst that extended from the floor of the mouth to the midline of the neck. Ultrasonography revealed a fluid-filled sublingual mass. Magnetic resonance imaging performed when the patient was 1 week old demonstrated a 2-cm, cystic, left-sided, sublingual mass that crossed the midline without extension inferior to the mylohyoid muscle. At 3 months of age, the patient developed a 1-cm, solid, submental mass. At the time of surgery, the lesion had a fibromembranous tract that extended through the myolohyoid muscle to a 1-cm cyst in the submental region. Histologic sections depicted 2 dermoid cysts and a connecting fistula. This case represents the first report (to our knowledge) of a dermoid cyst presenting in a neonate as a mass in the floor of the mouth with extension to the midline of the neck.