What is a sebaceous cyst?
This article describes the cysts that have been historically called sebaceous cysts because of a wrong belief they all arise from the sebaceous glands, which is now known not to be true. These cysts include:
- Sebaceous cyst
- Epidermoid cyst
- Pilar or trichilemmal cyst or wen
All three types of cysts have similar symptoms and treatment.
Sebaceous, pilar and epidermoid cysts look like dome-shaped lumps, from few millimeters to several centimeters in size. They are firm, movable, with smooth surfaces, nontender, painless, sometimes itchy and covered by a normal, white or yellow skin [2,3]. They may have a rancid smell or ooze a greasy material . When inflamed, they are usually tender, painful and covered by a red skin .
These cysts can be found mainly in middle-aged adults and rarely in children . They grow slowly, so they tend to increase in size over the months or years, but they can heal on their own.
Appearance. A sebaceous cyst can have a small opening, which allows squeezing out the greasy material.
Picture 1. A large sebaceous cyst on the back of the hand (source: ResearchGate, CC licence)
Risk factors include swollen hair follicles, high levels of the hormone testosterone and use of androgenic anabolic steroids .
Locations: anywhere in the skin (except on the palms and soles), but mainly on the scalp, ears, face, back and upper arm .
Origin. Epidermoid cysts arise from the epidermal cells from the the skin surface or the uppermost part of the hair follicle (follicular infundibulum) .
Appearance. An epidermoid cyst appears as a firm lump, which can be covered by normal, white, yellowish or dark brown skin–especially in individuals with darker skin, such as Indians. It can have a blackhead-like opening in the middle, which can ooze a white greasy material [6,7].
Picture 3. An epidermoid cyst with two blackhead-like openings (source: Samuel Freire da Silva, MD, Atlasdermatologico.com.br)
Locations: on the face, scalp, behind the ear, neck, upper back or chest, shoulders, arms and armpits, less commonly in the lips, tongue, eye, breasts, scrotum, vagina, labia or elsewhere in the body .
Risk factors include acne, trauma, surgery, exposure to UV light or sun, an infection with the Human papillomavirus (HPV) and genetic predisposition [5,6].
Milia are small (1-2 mm) white epidermoid cysts on the face, mainly in newborns, children and adolescents .
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.
Favre-Racouchot syndrome refers to the development of the epidermoid cysts in the elderly due to accumulated sun exposure .
Gardner’s syndrome includes multiple epidermoid cysts, fibromas and lipomas, osteomas and polyps of the colon.
Pilar (Trichilemmal) Cyst
Origin. A pilar or trichilemmal cyst arises from the outer sheath of the hair follicle . It is filled mainly with the protein keratin .
Risk factors. Pilar cysts tend to run in families, so if other family members have them, you are at increased risk, too .
Appearance: a lump with no opening .
Picture 2. A pilar cyst on the scalp (source: DermNetNZ, CC licence)
Locations: mainly on the scalp, also in the scrotum or elsewhere .
Chart 1. Sebaceous vs Pilar vs Epidermoid Cyst
|Origin||Sebaceous gland||Hair follicle infundibulum (upper part of the hair follicle)||Hair root (bottom part of the hair follicle)|
|Common locations||Face, upper back||Face, ear, neck, upper back, chest||Scalp, scrotum|
|Development into cancer||Very rarely||Very rarely||Very rarely|
Common Cyst Locations
Picture 4. A. A small epidermal cyst above the base of the nose. B. After cyst removal
(source: Archives of Plastic Surgery, CC licence)
Front of the Neck
Picture 5. A. A small epidermal cyst at the front of the neck. B. A small scar after the cyst removal
(source: Archives of Plastic Surgery, CC licence)
Back of the Neck
Picture 6. An inflamed epidermoid cyst at the back of the neck
(source: Steven Fruitsmaak, Wikimedia, CC licence)
Behind the Ear
Picture 7. A sebaceous cyst behind the ear
(source: Klaus D. Peter, Wikimedia, CC licence)
Picture 8. An epidermoid cyst on the earlobe
(source: Wikimedia, CC licence)
Lumps that can look similar as sebaceous, epidermoid or pilar cyst:
- Swollen lymph node (in the neck, armpits or groin)
- Lipoma (at the shoulder girdle level)
- Dermoid cyst
- Ganglion cyst (near the wrist or other joints)
- Digital mucous cyst (a small bump on a finger)
- Pilonidal cyst (in the tailbone area)
- Bartholin’s cyst in the vagina
How to pop a sebaceous cyst?
- Keep a warm moist compress on the cyst for one hour.
- Wash the hands.
- Disinfect the overlying skin with an disinfectant, such as povidone-iodine.
- Using the fingers (but not the nails) and a gauze, keep squeezing the cyst until all the greasy material comes out. If nothing comes out after applying a moderate effort, do not squeeze vigorously and do not make any cuts or punctures in the skin to avoid the risk of infection, bleeding or nerve injury.
- Clean the skin with warm water and disinfectant.
- Place a bandage over the opening.
After squeezing, the cyst can build up again within several weeks or months.
Surgical Removal of the Cyst
Surgical techniques used in treatment of a sebaceous cyst :
- A short incision and drainage is performed without removal of the cyst’s wall. After this procedure a cyst often recurs.
- A minimal excision technique includes a short (2-3 mm) incision, expression of the cyst content and removal of the cyst wall. The cut may need no suturing.
- Laser is used to make a small hole through which the content is squeezed. A month later, the cyst wall is removed . This technique produces only a minimal scar.
- Conventional wide excision includes a longer incision (probably >1 cm), removal of the cyst content and wall and closing with several sutures. This procedure leaves a thin scar.
Video 1. A surgical excision (removal) of a sebaceous cyst on he scalp
Warm compress applied for 20 minutes can soften sebaceous cyst and thus make it easier to pop.
There seems to be no convincing evidence about the effectiveness of aloe vera, apple cider vinegar, bee pollen, castor oil, Epsom salt, tea tree oil, turmeric and other home remedies in treatment of sebaceous cysts.
Cysts that have been only squeezed, but the cyst wall has not been removed, often recur within few months.
Inflammation and Infection
A cyst can get inflamed or infected from no obvious reason. An inflamed or infected cyst is usually tender or painful and covered with a red skin (Picture 9).
Doctors usually leave an inflamed or infected cyst for a weak until the inflammation decreases, before they treat it, because it is easier to remove and close [4,5]. An inflamed cyst can be treated by an injection of the steroid triamcinolone  and an infected cyst with topical or oral antibiotics.
Picture 9. An infected epidermoid cyst below the jaw
(source: Primary Care Dermatology Society, by permission)
A big cyst, especially on the scalp can burst. A rupture causes a skin wound with irregular borders, which will likely leave a visible scar. A ruptured cyst is prone to infection, so it needs to be treated promptly.
Sebaceous , pilar  and epidermoid  cysts do not spread to other body locations and very rarely develop into skin cancers. Skin cancer can look as a bump with a red ulcer in the middle and usually develops on the sun-exposed skin on the face or neck.
In general, there is no known way of prevention of sebaceous cysts. Keeping acne under control, can reduce the risk of sebaceous cyst, though .
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- Epidermal inclusion cyst, overview Emedicine
- Epidermoid and Pilar Cysts (Sebaceous Cysts) Patient.info
- Wu HuiLing et al, 20019, A New Procedure for Treating a Sebaceous Cyst: Removal of the Cyst Content with a Laser Punch and the Cyst Wall with a Minimal Postponed Excision PubMed Central
- Kapadia A, 2014, Pilar cyst DermNetNZ.org
- Abreu Velez AM et al, 2011, An inflamed trichilemmal (pilar) cyst: Not so simple? PubMed Central
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