OVERVIEW

What is a dermoid cyst?

A dermoid cyst, also known as a congenital inclusion dermoid cyst, is a benign congenital subcutaneous lesion.

Caused by abnormalities during fetal development, the cyst contains squamous epithelium and other skin structures (such as hair follicles, sweat glands, and sebaceous glands). It is almost always present at birth and grows slowly.

It typically appears during infancy or childhood as a firm, fixed or freely movable nodule (usually 0.5–5 cm in size). Most commonly found around the orbit, it may also occur on the scalp and other areas.

Surgical removal is recommended, with the timing of excision depending on the location and associated symptoms.

SYMPTOMS

What are the manifestations of dermoid cysts?

Dermoid cysts are firm nodules located in the dermis or subcutaneous tissue. However, palpation may vary depending on the location, thickness of the overlying skin, cyst size, or the specific tissue composition within the cyst. Previous infections may also affect the texture.

They can occur anywhere on the body surface but are commonly found along the midline of the head, face, neck, abdomen, and back, particularly around the orbit, lateral eyebrow, nasal bridge, and oral cavity floor.

Most cases are present at birth, with the majority diagnosed before the age of 5, though some may not be discovered until over 60 years old. Initially, they may be imperceptibly small, asymptomatic, and grow slowly until inflammation or trauma draws attention (Figure 1).

Most are solitary, typically 0.5–5 cm in diameter (occasionally larger), and may protrude as hemispherical elevations. Some adhere to underlying tissues, while others remain mobile. These nodules are non-pulsatile, non-compressible, painless, opaque, and skin-colored or bluish.

Unless dimpling, sinuses, or fistulas are present, the overlying skin appears normal. A tuft of hair in a dimple may indicate an underlying fistula.

What complications can dermoid cysts cause?

Cysts may develop dimples, sinuses, or fistulas. Sinuses are blind tracts opening superficially, while fistulas connect the cyst to the skin surface or deeper structures (e.g., bone, CNS, or paranasal sinuses).

• The most common complication is infection, including meningitis if the cyst communicates with the CNS.

• Scalp cysts may adhere to the periosteum or erode the underlying skull.

• Nasal dermoid cysts often enlarge, damaging the nasal bones.

• Although very rare, malignant transformation can occur.

• Midline lesions (especially in the lumbosacral region) often suggest spinal dysraphism, including tethered cord syndrome.

Can dermoid cysts become cancerous?

Dermoid cysts are benign congenital subcutaneous lesions. Malignant transformation is rare but possible.

CAUSES

What causes dermoid cysts?

Dermoid cysts originate from the ectoderm and are caused by localized developmental abnormalities during embryogenesis. They typically occur along embryonic fusion lines (the midline of the body) or within the neural axis. The cyst wall is composed of stratified squamous epithelium and contains epidermal appendages.

On the face, they usually appear above the lateral end of the eyebrow (lateral angular dermoid cysts) or at the root of the nose. They may also develop along the midline of the forehead, above the mastoid process, the floor of the mouth, or anywhere along the scalp midline from the forehead to the occiput. Additionally, they can occur on the chest, back, abdomen, and perianal region.

Nasal and lateral angular dermoid cysts have been observed in multiple members of the same family, suggesting a genetic association.

DIAGNOSIS

How should a suspected dermoid cyst be diagnosed?

Clinical diagnosis can be made based on the cyst's location and symptomatic characteristics. A biopsy is usually required for confirmation.

What conditions should be differentiated from a dermoid cyst?

• Differentiation from epidermal cysts.
  The cyst wall of a dermoid cyst is also composed of stratified squamous epithelium, but unlike epidermal cysts, its wall resembles follicular infundibular cells with a granular layer. The cyst cavity contains keratinocytes arranged in a reticular or lamellar pattern, and the cyst wall also contains mature hair follicles and sebaceous glands, often with hair-containing follicles protruding into the cyst.
  In the adjacent dermis, sebaceous glands and eccrine sweat glands are frequently present, and occasionally apocrine sweat glands may also be observed. If the cyst ruptures, a foreign body reaction may occur.

• Differentiation from true teratomas. Teratomas may sometimes involve the skin, but they can be distinguished histologically by their contents. Teratomas often involve more than one germ layer, whereas dermoid cysts contain only ectodermal components.

TREATMENT

Which department should I visit for a dermoid cyst?

If you suspect a dermoid cyst, you can visit the dermatology and venereology department or general surgery department. Depending on the location, you may also consult ophthalmology or otolaryngology.

If the dermoid cyst shows signs of depression, ulceration, or rapid enlargement, prompt medical attention is necessary.

How is a dermoid cyst treated?

Due to the risk of complications, dermoid cysts should be surgically removed. The timing of removal depends on the location and other related symptoms.

Dermoid cysts occurring along the cranial fissure plane in children (including the midline of the back) should not be surgically excised or biopsied until assessed for potential connections with the spine or intracranial structures.

CT or MRI scans can aid in diagnosis. Any subosseous lesions detected by CT must be further evaluated with MRI, as CT scans may sometimes fail to confirm cranial penetration. If intracranial involvement is detected, the patient must be referred to neurosurgery.

DIET & LIFESTYLE

Does a dermoid cyst affect diet and daily life?

No, you can maintain normal eating habits and daily routines.

• Avoid frequently squeezing the dermoid cyst;

• Monitor changes in the cyst. Seek medical attention promptly if abnormalities occur, such as rapid enlargement, rupture, pain, or infection;

• Maintain a healthy, balanced diet, quit smoking and alcohol, and strengthen physical exercise to boost immunity.

Does a dermoid cyst surgery affect diet?

No. Most dermoid cyst surgeries are performed under local anesthesia, allowing normal eating immediately after the procedure.

PREVENTION

Can dermoid cysts be prevented?

No, they cannot.

Since dermoid cysts originate from the ectoderm and are caused by localized embryonic dysplasia, they are congenital and thus cannot be prevented.

How to identify dermoid cysts early?

• Learn about dermoid cysts and their associated symptoms;

• If you notice localized skin lumps on your child's body, seek medical attention promptly for diagnosis.