Last Updated on September 11, 2023
A dermoid cyst of skin is a slow-growing cystic mass that is lined by epithelium [skin] and is filled with old skin cells that are grossly seen as pultaceous or toothpaste-like material.
It arises due to the entrapment of ectodermal elements. [Ectoderm is the outermost of the three primary germ layers of an embryo. It gives rise to structures such as the epidermis, the nervous system, the brain, parts of the eyes, and ears.]
The term dermoid cyst may represent a lesion across various systems of the body. It may refer to
- Cystic lesion of the skin
- Cyst in the spine or skull
- Cyst in the ovary
All these lesions have a similar histology of a lining of the dermis that contains stratified squamous epithelium with hair follicles and sebaceous glands and a cavity that contains keratin, a type of protein.
Sites of Dermoid Cysts
Dermoid cysts can occur anywhere on the body. These can be cutaneous – those which are present under the skin or non-cutaneous.
Cutaneous
- Face
- Neck
- Scalp
Non-cutaneous
- Intracranial
- Intraspinal
- Perispinal
- Intra-abdominal cysts
- Ovary
- Omentum [peritoneal fold]
Cutaneous Dermoid Cysts
A cutaneous dermoid cyst is a developmental anomaly that occurs due to the entrapment of ectodermal elements along the lines of embryonic closure.
These are derived both from ectoderm which forms stratified squamous epithelium and mesoderm which results in adnexal structures like hair, and glands.
Dermoid cysts are considered to represent up to about 60 percent of scalp and skull masses in children.
Most of these lesions are congenital but often not diagnosed at birth as they may appear late.
The lateral aspect of the upper eyelid is the most common region of the occurrence. These occur less commonly in the mid-chest region, sacrum, and perineal area.
Though considered congenital, only about 40 percent of them are diagnosed at birth, while the rest are diagnosed by 5 years of age. Some cases may occur in adulthood too.
More than 80 percent of these cysts occur in the head and neck region.
The cause is not clearly known.
They are thought to occur because of abnormal sequestration and the inclusion of the surface ectoderm along the lines of skin fusion during embryologic development.
Microscopic examination of dermoid cyst shows
- A well-defined wall lined by stratified squamous epithelium
- A cavity that is filled by structures originating from mesoderm
- Hair follicles
- Sebaceous glands
- Eccrine glands
Clinical Presentation
The cutaneous dermoid cyst is usually a flesh-colored, noncompressible subcutaneous nodule. It is usually not tender to touch.
The protrusion of hair is pathognomonic. The cysts may lie dormant for a long period and then enlarge resulting in clinical manifestation.
Midline cysts have the highest association with cranial or spinal dysraphism. These are also more likely to have intracranial extension.
Multiple cysts have also been reported.
Imaging
The diagnosis is mostly made on a clinical basis. Imaging has a role in identifying any bony erosion due to mass effect. It is also useful for diagnosing intracranial or intramedullary cysts and gauging neurological insults.
Bony erosion is better determined by CT or X-ray though the latter would miss small changes.
MRI is useful in case of neural involvement.
Treatment
The definitive treatment of a dermoid cyst is surgical.
Small cysts do not require immediate excision as the cyst can be stable for a long time.
When the cyst is growing, it should be removed before complications like rupture, etc. occur.
As far as possible, the cyst should be removed in totality. Sometimes, partial removal needs to be done when the cyst is attached to some viral structure.
Complications
- Infection
- Suppuration
- Bursting
- Ulceration
- Pressure symptoms to the surrounding structures
Differentiation from Other Similar Types of Cutaneous Cysts
Some other cysts may seem like dermoid cysts and there is often confusing literature available using interchanging names and nomenclature. For example, some articles consider epidermal inclusion cysts or sebaceous cysts the same as dermoids but there is a difference at the histological level and we will discuss that now.
Epidermal Inclusion Cyst
Epidermal inclusion cyst is also widely known as sebaceous cyst or epidermoid cyst. Because of the similarities of the names, dermoid and epidermoid cysts may be thought to represent one entity.
It is called sebaceous cyst because it contains material that was deemed to be sebum. But it is actually a misnomer as the material is formed of keratin.
The cyst appears similar clinically and this further complicates the matter.
Epidermal inclusion cyst is different from dermoid cyst and the difference is based on histological features. Both contain epidermal lining but adenaxal structures from mesoderm are not present in epidermal inclusion cyst. It just contains keratin that gives an appearnce similar to sebum.
Trichilemmal Cyst
It is also known as a pilar cyst. Trichilemmal cyst is a keratin filled cyst that takes origin from hair root sheath. It is commonly seen in scalp.
It has stratified squamous epithelium lining and contains keratin. The treatment is excision.
Noncutaneous Dermoid Cysts
Dermoid Cysts can occur anywhere in the body. Apart from skin, the main sites of occurrence are
- Ovary
- Spine
- Epibulbar – on the eye
- Intracranial
- Intraabdominal
- Nasal Sinus
- Floor of the mouth
- Testes
Ovarian dermoid cyst is a cystic tumor of the female ovary, also called cystic tertoma. A teratoma contains formations from endo, mesoderm. Therefore ovarian dermoid can contain teeth, skin, hair, muscle and fat.
Cystic teratoma is a less common tumor and often occur in females of second to 4th decade.
Noncutaneous dermoids may be symptomless or produce symptoms depending on the location and pressure effect.
For example, ovarian cyst may lead to vague pelvic pain, swelling and/or bloating. Spinal or cranial cysts may present with neural symptoms.
Work up and treatment is dependent on the location of the cyst. Intracranial and spinal cysts could be difficult to excise.
References
- Prior A, Anania P, Pacetti M, Secci F, Ravegnani M, Pavanello M, Piatelli G, Cama A, Consales A. Dermoid and Epidermoid Cysts of Scalp: Case Series of 234 Consecutive Patients. World Neurosurg. 2018 Dec;120:119-124. [Link]
- Sorensen EP, Argobi Y, Au SC, Goodarzi M, Rosmarin D. Multiple subcutaneous dermoid cysts. Cutis. 2019 May;103(5):E17-E18. [Link]
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Menke J, Schwarz A. Ovarian dermoid cyst with teeth. BMJ Case Rep. 2013 Aug 7;2013:bcr2013010271. [Link]