Ultrasound of Sublingual Dermoid Cyst

In this radiology lecture, we review the ultrasound appearance of sublingual dermoid cyst and explain floor of mouth anatomy!

Key teaching points include:

The floor of the mouth is a horseshoe-shaped area beneath tongue and in between sides of mandible, inferiorly bounded by mylohyoid muscle, and containing sublingual space (SLS)
SLS medial border: Midline genioglossus/geniohyoid muscle complex; SLS inferolateral border: Mylohyoid muscle
Anterior margin of hyoglossus muscle projects into posterior SLS
Sublingual dermoid cyst is a rare, benign cyst with squamous epithelial lining and contains skin appendages
Dermoid and epidermoid cysts are in same family, terminology often used interchangeably, although epidermoid cysts less common and tend to contain fluid contents only
Dermoid cyst mean age of presentation late teens to twenties, average age 30
Presents as a slowly enlarging neck mass, may cause dysphagia
Often round or oval in shape and homogeneously hypoechoic with punctate echogenic foci
May have pathognomonic “sack of marbles” appearance
Relationship to mylohyoid is key for surgical planning: Intraoral resection for sublingual (above mylohyoid) location, extraoral approach for submental/submandibular (below mylohyoid) location
Most cysts are midline
DDx: Suprahyoid thyroglossal duct cyst, ranula (simple and diving), abscess and lymphangioma