Floor of mouth dermoid cyst

Case contributed by Alasdair Grenness


24 hours of dysphagia and dysarthria due to superior displacement of the tongue on a background of six months of progressive submental swelling.

Patient Data

Age: 30 years
Gender: Female

Clinical photography revealing bilateral floor of mouth swelling with displacement on tongue and submental swelling.


There is a unilocular low-density cystic mass centered upon the sublingual space which measures up to 5.4 x 5.1 x 6.1 cm (TR x AP x CC). The mass has subtle wall enhancement and an internal density of 15-20HU.

The mass appears centrally positioned between the two genioglossus muscles, splaying the genioglossus and mylohyoid muscles laterally on either side. Both submandibular glands are seen separately and are normal in appearance. Superiorly the mass displaces the tongue and contacts the uvula posteriorly but the oropharyngeal airway remains patent. Anteriorly the mass abuts the mandible. Inferiorly the mass abuts but does not extend beyond the hyoid. There are no overlying inflammatory changes evident


A large centrally located lesion lying within the sublingual space. It demonstrates hypointense T1 signal and homogeneously high T2 signal. It is well circumscribed and mildly lobulated. On the post-contrast sequences, it has thin, smooth peripheral enhancement. No internal or nodular enhancing component is identified. There is mild signal reduction on the fat-saturated sequence suggesting an element of fatty content. No macroscopic fat is detected.

Although presenting with dysarthia and dysphagia the patient was clinically well with no local or systemic signs or symptoms of infection or signs of upper airway obstruction. Clinical examination revealed a soft but edematous floor of mouth bilaterally with superior displacement of the tongue and a large soft submental swelling. A flexible nasendoscope revealed a patent airway despite displacement of the tongue. 

An attempt to aspirate the swelling through the floor of mouth yielded only a small amount of sebaceous like material. A subsequent CT Neck and MRI revealed a 5x5x6cm unilocular low density cystic mass occurring in the sublingual space between the two genioglossus muscles with the possibility of a dermoid cyst. 

Consideration for an intraoral, external or combined surgical approach was made, and the patient subsequently proceeded to an external approach given the large submental component whereby an intact cyst was resected. Histopathology revealed an epithelial lined cyst with sebaceous glands and hair follicular structures consistent with a dermoid cyst. The patient subsequently made a full recovery.


Histopathology slide 1: Low power (x4) view showing the cyst wall lined by stratified squamous epithelium.

Histopathology slides 2 and 3: Intermediate power (x10) and high power (x20), both showing the diagnostic features of dermoid cyst with presence of sebaceous glands and hair follicular structures in the soft tissue adjacent to the epithelium.

Case Discussion

Dermoid cysts are cysts filled with sebum like material with evidence of specialized skin derivatives 1. Floor of mouth dermoid cysts account for 1.6% of all dermoid cysts 2 and they usually present as a midline symmetrical slowly enlarging lesion. Cysts superficial to geniohyoid may cause posterosuperior displacement of the tongue, dysphonia, dysphagia 3 or airway obstruction 4. While cysts inferior to geniohyoid can cause submental swelling 3

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