Dermoid Cysts of the Neck

A dermoid cyst is a benign, congenital cyst that forms when layers of skin become trapped between deeper tissues during development. In the neck, it is mostly located in the midline, under the chin or in the floor of the mouth. It grows slowly, is usually painless and is most often noticed in childhood or young adulthood.

What is a dermoid cyst?

In the womb, the face and neck are formed by layers of tissue arriving from different directions and fusing in the midline. If some skin tissue remains deep inside during this fusion, an enclosed sac develops over time. Because the inner lining of the cyst resembles skin, it collects oil, sweat and keratin inside; hair follicles and sebaceous glands are sometimes present as well. The slow accumulation of this content causes the cyst to grow over the years. Dermoid cysts of the neck are seen most often in the floor of the mouth and the area under the chin, and less often in the lower midline of the neck.

Symptoms

• A slowly growing, doughy, painless lump under the chin or in the midline of the neck
• With cysts in the floor of the mouth, fullness under the tongue and the tongue being pushed upwards
• With large cysts, difficulty speaking, chewing or swallowing
• With cysts under the chin, a “double chin” appearance
• Redness, pain and tenderness when it becomes inflamed

Unlike thyroglossal duct cysts, dermoid cysts do not move noticeably on swallowing or with tongue movement; this distinction is a useful guide on examination.

Diagnosis

On examination, the position, consistency and immobility of the cyst are assessed. Ultrasound shows the borders of the cyst and the dense, fat-like content inside it. For cysts in the floor of the mouth, magnetic resonance imaging (MRI) or computed tomography (CT) is often requested, because the position of the cyst relative to the muscles under the tongue determines the surgical approach. The differential diagnosis includes thyroglossal duct cysts, salivary gland cysts (ranula) and enlarged lymph nodes; if necessary, a sample is taken with a fine needle.

Treatment

Dermoid cysts do not regress on their own and keep growing as their content accumulates. The treatment is surgical removal of the cyst in one piece, together with its wall. Depending on the position of the cyst, the operation is performed through the mouth or through a skin incision under the chin; when the approach through the mouth is used, no scar is left on the skin. Removing the cyst wall intact prevents the content from spreading into the surrounding tissue and prevents recurrence. The procedure is performed under general anaesthesia.

What to expect after surgery

Mild pain and swelling lasting a few days are normal after surgery. After operations through the mouth, soft and lukewarm foods are recommended in the first days; tongue movements return to normal in a short time. Because a skin incision is placed in the crease under the chin, the scar fades over time. When the cyst is removed completely, recurrence is not expected. The removed tissue is sent for pathological examination and the result is discussed at the follow-up visit.

When should you see a doctor?

• If you have noticed a lump under the chin or in the midline of the neck that is growing, even slowly
• If there is fullness under the tongue or a change in speech or swallowing
• If the lump is becoming red, painful or suddenly enlarging