Paediatric submental epidermoid cyst

Abstract

A young girl presented with an insidious onset, gradually increasing midline submental swelling of 1-year duration and pain on swallowing for 6 months. Ultrasonography of the neck suggested a hypoechoic cystic swelling of the submental region between the muscles of the floor of the mouth, with no increased vascularity. An extraoral surgical enucleation was done and a postoperative biopsy suggested an epidermoid cyst. Epidermoid cysts of the submental region are extremely rare and any midline head and neck lesion in children requires critical examination and evaluation to avoid complications. Here, we present a rare case of a paediatric submental epidermoid cyst and its clinical features and management.

Background

Epidermoid cysts are cystic lesions lined by squamous epithelium. Epidermoid cysts are rare in the head and neck region. The most common site in the head and neck region is the submental region. It is extremely rare in children. In this case report, we are discussing a rare case of a paediatric submental epidermoid cyst.

Case presentation

A young girl presented with swelling in the submental region which was insidious in onset and gradually increased in size over 1 year. She reported pain during swallowing for the last 6 months. There was no history of breathing difficulty, dysphagia or discharge from the swelling. There was no history of trauma or previous surgery. She had no known comorbidities. On examination, there was a 1.5×1.5 cm single midline cystic swelling in the submental region that had a smooth surface and regular margin. It was not mobile in any direction. There was no local rise in temperature or tenderness. It became prominent on protrusion of the tongue. There was no evidence of any transillumination. Cervical lymph nodes were not palpable. Oral cavity and oropharyngeal examinations were normal (figure 1).

Figure 1.

(A) Anterior view and (B) lateral view of the neck with the black arrows showing the submental cyst.

Investigations

Basic preoperative blood investigations were normal. Ultrasonography (USG) of the neck suggested a hypoechoic midline cystic lesion measuring 2×1×2 cm between muscles of the submental region. Vascularity was not demonstrated on Doppler images (figure 2).

Figure 2.

(A) Ultrasonography of the neck showing a hypoechoic 2×1×2 cm cystic lesion in the submental region. (B) Doppler to see the vascularity of the lesion.

Differential diagnosis

The most common differential diagnoses for submental swellings are submental infective lymphadenopathy, plunging ranula, dermoid cyst, epidermoid cyst, lipoma, suprahyoid thyroglossal cyst, lymphangioma and haemangioma.

Treatment

The cyst was excised in toto under general anaesthesia. A horizontal incision was given in the submental region over the cyst and subplatysmal flaps were raised superiorly and inferiorly. Bilateral anterior bellies of digastric muscles and the mylohyoid muscle were identified. The mylohyoid muscle was dissected and the cyst was found between the mylohyoid and geniohyoid muscles. The cyst was excised in toto and the wound was sutured in three layers (figure 3).

Figure 3.

(A, B) Intraoperative images of the epidermoid cyst excision.

Outcome and follow-up

There were no intraoperative complications. The postoperative biopsy suggested an epidermoid cyst. It was a 2.1×2×1 cm cyst filled with creamy white pultaceous material. Microscopic examination showed a cystic lesion lined by acanthotic stratified squamous epithelium displaying preserved granular layer and enclosing lamellated flakes of keratin. She did not have any difficulties in swallowing or speech postoperatively.

Discussion

Benign cystic lesions lined by simple squamous epithelium are defined as epidermoid cysts.¹ Epidermoid cysts can be congenital or acquired.² Congenital cysts are derived from epithelial debris or rests that get embedded during the closure of bilateral first and second branchial arches.³ Acquired cysts are derived from epithelial cell implantation iatrogenically or during trauma.⁴ They account for only 1.6%–6.9% in the head and neck region and oral cysts constitute less than 0.01%.⁵ Submental epidermoid cysts are rare in the head and neck region, especially in children, and can clinically and radiologically mimic many other midline swellings like lipoma, dermoid cyst, suprahyoid thyroglossal cyst, plunging ranula, lymphangioma, haemangioma and submental infective lymphadenopathy due to oral infections.^{6 7}

On MRI, epidermoid cysts appear hypointense on T1-weighted images and hyperintense on T2-weighted images due to increased keratin content, whereas the dermoid cyst appears hyperintense on both T1-weighted and T2-weighted images due to increased lipid content.⁸ In USG, the dermoid cyst may give a ‘bag of marbles’ appearance depending on the consistency of the contents.⁹

In children, USG is an ideal imaging modality as it causes no radiation exposure, and it can differentiate an epidermoid cyst from vascular lesions preventing unwarranted intraoperative and postoperative complications.¹⁰ Even though MRI seems to be a superior imaging modality compared with USG in differentiating dermoid and epidermoid cysts, USG is easily available, feasible and cost-effective, making it the first line of imaging and often the only imaging required. This is especially true in resource-constrained countries. The gold standard for diagnosing epidermoid cyst is histopathology. Histopathologically, it is a cyst lined by squamous epithelium and filled with keratin.

The best management for the epidermoid cyst is surgical excision with an intact cyst wall as it can reach large proportions that can cause dysphagia and respiratory distress.¹¹ The approach for the excision can vary according to the location and size of the cyst. When the cyst is below the geniohyoid muscle, an extraoral approach is warranted, while an intraoral approach is used for cysts above the geniohyoid along the floor of the mouth.¹² Ultrasound can identify the plane of the swelling. In our patient, ultrasound suggested that the cyst was between the mylohyoid and geniohyoid muscles. Hence, the swelling was excised by the extraoral route. Recurrence of epidermoid cysts is rare.⁷ The epidermoid cyst rarely undergoes a malignant transformation.¹³ The postoperative period is usually uneventful.

In conclusion, ultrasound with Doppler is a very useful tool not only to characterise submental swellings but also to plan the most appropriate surgical access to avoid unnecessary intraoperative and postoperative complications.

Patient’s perspective.

I (father of the patient), was apprehensive regarding the future of my daughter and the consequences of such a swelling in the neck. I was worried about its effect on swallowing, speech and breathing. I am extremely thankful that the surgery was successful and it turned out to be a benign lesion with less chances of recurrence. Post operatively the scarring is minimal and my daughter has a normal life.

Learning points.

• Although epidermoid cyst in the head and neck region is rare in the paediatric age group, it should be considered in the differential diagnoses for submental swellings.

• An ultrasonography of the neck along with Doppler can be used as a diagnostic tool in economically constrained countries. It avoids radiation exposure, especially in children. It is also a safe and low-cost imaging modality.

• Enucleation of the cyst with an intact cyst wall can prevent recurrence.

• The surgical access of the cyst can be intraoral or extraoral depending on its location in relation to the neck muscles and its size.

Ethics statements

Patient consent for publication

Parental/guardian consent obtained.