There is a well defined mass lesion of high T1 signal intensity. The signal is suppressed on fat-suppressed STIR sequence indicating its fatty nature. This would be in keeping with a dermoid cyst (or possibly a lipoma). This mass lesion extends posteriorly into the submandibular space where it displaces the right submandibular gland inferiorly. The adjacent mandible is normal.
Histological examination showed the lesion contained fat.
Reference: Kelly K. Koeller, Leonor Alamo, Carol F. Adair, and James G. Smirniotopoulos From the Archives of the AFIP: Congenital Cystic Masses of the Neck: Radiologic-Pathologic Correlation RadioGraphics 1999; 19: 121.
Credit: Dr Abhijit Datir