Dermoid of the oral cavity: case report with histopathology correlation and review of literature

Abstract

Dermoid cysts are rare masses of the oral cavity derived from ectodermal elements. These are benign, slow-growing tumors that are typically asymptomatic but cause complications of inflammation or dysphagia, dystonia, and airway encroachment due to mass effects. We report the case of a 17 year old female with a painless mass in the left side of the oral cavity. Ultrasound findings demonstrated non-specific findings of a cystic lesion, and definite diagnosis was made with contrast-enhanced CT and intraoperatively with pathologic confirmation. This retrospective report highlights the challenges in evaluating masses of the oral cavity with imaging and provides a comprehensive discussion on imaging of oral masses on various imaging modalities to guide diagnosis and management.

Dermoid Cyst of the Floor of the Mouth: Diagnostic Imaging Findings

“…Diagnostic imaging can reveal intracystic floating corpuscles (i.e., the “sack of marbles” sign) which are usually hypodense on CT scans, hyper/hypointense on T1-weighted MRI and hypointense on T2-weighted MRI scans because of their lipid contents, the presence of which is pathognomonic for a dermoid cyst [ 2 , 4 , 7 ]; the “marbles” can be calcified, as in the present case. Because of dense cystic fluid, a percutaneous fine needle aspiration may be not recommended [ 6 ].…”

“…They can be simple or plunging in the submandibular space extending through a defect in the mylohyoid muscle (i.e., the boutonniere) or because it ruptures posteriorly. Evidence of a beak of the cyst towards the sublingual space (tail sign) is considered typical of ranulas [ 4 , 8 ]. However, a dermoid cyst entirely confined within the sublingual space cannot be distinguishable from a ranula by imaging findings alone [ 7 ].…”

“…Dermoid cysts are slow growing and painless masses; when large enough, they can cause dysphagia, dysphonia, and dyspnea [ 4 ]. Diagnostic imaging plays a pivoting role in the anatomic localization of the mass in the floor of the mouth and, therefore, helps in guiding surgical planning [ 5 - 7 ].…”

Large Dermoid Cyst of the Floor of the Mouth - An Emphasis on Differential Diagnosis

“…Imaging studies are important to assist in the differential diagnosis, but may be difficult with dermoid cysts and ranulae, as both appear as thin-walled, cystic lesions, which are hypodense on CT and can present with high-intensity on T2weighted images on MRI 9 . Nevertheless, each have certain distinguishing characteristics, such the "sack of marbles" appearance that is pathognomonic for dermoid cysts, caused by areas of fat attenuation on CT 10 .…”

“…Nevertheless, each have certain distinguishing characteristics, such the "sack of marbles" appearance that is pathognomonic for dermoid cysts, caused by areas of fat attenuation on CT 10 . Additionally, plunging ranulae may demonstrate a thin "tail" of fluid from the collapsed sublingual space that appears to dive into the submandibular space on imaging; this sign can occasionally be seen on CT and MR imaging, and can be an important diagnostic clue when visualized 9,10 . In the present case, the appearance on CT and MRI imaging reports misdiagnosed the lesion as a ranula.…”