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

To learn more about the Samsung RS85 Prestige ultrasound system, please visit: https://www.bostonimaging.com/rs85-prestige-ultrasound-system-4
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