These are small bumps that develop just beneath the skin on your face, neck, trunk and sometimes your genital area. They are slow-growing and often painless. Although many people refer to epidermoid cysts as sebaceous cysts, true sebaceous cysts are much less common than epidermoid cysts.
Epidermoid cysts are almost always noncancerous, but in rare cases, they can give rise to skin cancers. Because this occurs so seldom, epidermoid cysts usually aren’t biopsied unless they have unusual characteristics that suggest a more serious problem.
Epidermoid cyst signs and symptoms include:
- A small, round bump under the skin, usually on the face, trunk or neck
- A tiny blackhead plugging the central opening of the cyst
- A thick, yellow, foul-smelling material that sometimes drains from the cyst
- Redness, swelling and tenderness in the area, if inflamed or infected
The surface of your skin (epidermis) is made up of an extremely thin, protective layer of cells that your body continuously sheds. Most epidermoid cysts form when these surface cells, instead of exfoliating normally, move deeper into your skin and multiply. Most often, this occurs in areas where there are small hair follicles and larger oil glands (sebaceous glands), such as your face, neck, upper back and groin. The epidermal cells form the walls of the cyst, and then secrete the protein keratin into the interior. The keratin is the thick yellow substance that sometimes drains from the cyst. This abnormal growth of cells may be due to a damaged hair follicle or oil gland in your skin.
Treatments and drugs
Small cysts that don’t cause cosmetic or functional problems are usually left alone. When a cyst is inflamed, gets bigger, is ruptured or infected, these treatment options exist:
- Incision and drainage: your doctor makes a small cut in the cyst and expresses the contents. Although incision and drainage is relatively quick and easy, cysts often recur after this treatment
- Total excision: The surgical excision removes the entire cyst and so prevents recurrence. Excision is most effective when the cyst isn’t inflamed. Your doctor may recommend first treating the inflammation with antibiotics, steroids, or incision and drainage and then waiting to perform excision for four to six weeks after inflammation resolves. Total excision requires sutures
A pilonidal cyst is an abnormal pocket originating in the skin that usually contains hair, skin debris and other abnormal tissue. A pilonidal cyst is almost always located near the tailbone at the top of the cleft of the buttocks. The term “pilonidal” comes from the Latin words for hair (“pilus”) and nest (“nidus”).
Pilonidal cysts affect men more often and most commonly occur in young adults. A pilonidal cyst may remain harmless. If it becomes infected, however, it will cause pain, inflammation and usually drainage of fluids. A pilonidal cyst may have no noticeable symptoms (asymptomatic). The only sign of its presence may be a small pit on the surface of the skin. When it’s infected, a pilonidal cyst becomes a swollen mass (abscess).
There is some disagreement about what causes pilonidal cysts. Most appear to form from loose hairs that penetrate the skin. Friction and pressure — skin rubbing against skin, tight clothing, cycling, long periods of sitting or similar factors — force the hair down into skin. Responding to the hair as a foreign substance, the body creates a cyst around the hair.