Epidermoid Cyst

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Published: February 25, 2017
Last reviewed: March 8, 2017

What is epidermoid cyst?

An epidermoid cyst is a benign (noncancerous) encapsulated lesion that arises from the epidermal cells on the skin surface or from the uppermost part of the hair follicle (follicular infundibulum) [3]. Its wall consists of the epidermal cells and its content mainly of the protein keratin and fat [2].

Synonyms for an epidermal cyst include keratin, epithelial, epidermal and follicular infundibular cyst [1,2].

Epidermoid and pilar cysts are more commonly, but technically wrongly, called sebaceous cysts.

Symptoms

An epidermoid cyst appears as a dome-shaped, firm or fluctuant, fixed lump from few millimeters to 5 centimeters in size, covered by normal, white, yellowish or dark brown skin [2]. It can have a blackhead-like opening, which can ooze a white or yellow greasy and rancid-smelling material [3,4].

Epidermoid cysts most commonly appear on the face, scalp, behind the ear, on the neck, upper back or chest, shoulders, arms, scrotum, vagina and labia [1,2]. Most epidermoid cysts appear in adults [3,6].

Epidermoid cyst

Picture 1. An epidermoid cyst with an opening (source: DermNetNZ, CC license)

Epidermoid cyst

Picture 2. An epidermoid cyst on the face (source: DermNetNZ, CC license)

Epidermoid cyst

Picture 3. An epidermal cyst on the earlobe (source: Wikimedia, CC license)

Epidermoid cyst

Picture 4. Two epidermoid cysts on the back (source: DermNetNZ, CC license)

Epidermoid cysts on the face (milia)Milia are small (1-2 mm) white epidermoid cysts on the face, mainly in newborns, children and adolescents [3].

Picture 5. Milia on the face of a child (source: DermNetNZ, CC license)

Epidermoid cyst at the back of the neck

Epidermal inclusion cyst is a type of epidermoid cyst, which develops from the cells of the surface skin layer (epidermis), when they are pushed into the deeper skin layer (dermis) during trauma or surgery, for example.

Picture 6. An inflamed epidermal inclusion cyst at the back of the neck (source: Steven Fruitsmaak, Wikimedia, CC license)

Epidermoid cysts and solar comedones on the faceFavre-Racouchot syndrome refers to the development of the solar comedones and epidermoid cysts in the elderly with a condition called elastosis and accumulated sun exposure [3,5].

Picture 7. Solar comedones and epidermoid cysts (Favre-Racouchot syndrome) (source: DermNetNZ, CC license)

Epidermoid cysts on the armGardner’s syndrome includes multiple epidermoid cysts, fibromas and lipomas, osteomas and polyps of the colon.

Picture 8. Multiple epidermoid cysts on the forearm as part of Gardner’s syndrome (source: DermNetNZ, CC license)

Infection

Infected epidermoid cyst below the jawAn infected epidermoid cyst is swollen, red, tender and painful.

Picture 9. An infected epidermoid cyst under the jaw (source: PCDS.org.uk, by permission)

Causes and Risk Factors

The exact cause of epidermoid cysts is not known. Risk factors include acne, trauma, surgery, exposure to UV light or sun, an infection with the Human papillomavirus (HPV) and genetic predisposition (for example, familial adenomatous polyposis) [2,3].

Differential Diagnosis

Other lumps that can look similar as an epidermoid cyst [2]:

Treatment

An epidermoid cyst can be removed by surgical excision. The removal of both the greasy content and the cyst wall is necessary for the cyst to be cured. There is no known prevention or home treatment for epidermoid cysts. If you only squeeze an epidermoid cyst, it will very likely recur in few weeks or months.

  • References

      1. Epidermal inclusion cyst, clinical presentation  Emedicine
      2. Zuber TJ et al, 2002, Minimal Excision Technique for Epidermoid (Sebaceous) Cysts  American Family Physician
      3. Epidermal inclusion cyst, overview  Emedicine
      4. Epidermoid and Pilar Cysts (Sebaceous Cysts)  Patient.info
      5. Feinstein RP, Favre-Racouchot Syndrome (Nodular Elastosis With Cysts and Comedones)  Emedicine
      6. Oakley A, Cutaneous cysts and pseudocysts  DermNetNZ

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