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A sebaceous cyst is a small, closed sac under the skin that contains oily or cheesy material. The cyst forms a smooth, firm bump or lump, most often on the face, scalp, neck, or middle of the body. A sebaceous cyst may occur if you have a blocked sweat gland or hair follicle. A sebaceous cyst that forms in the top layer of skin cells is called an epidermal cyst. If the cyst sac forms from hair follicle cells, it is called a pilar cyst. Having acne increases your risk for developing a sebaceous cyst.
Sebaceous cysts are pasty filled lumps or bumps that occur just below the skin is a closed sac under the skin filled with a cheese-like or oily material. Causes. Sebaceous cysts most often arise from swollen hair follicles.
- Are round cysts or small bumps that are easy to move with your fingers
- Are usually white or yellow, though people with darker skin may have pigmented cysts
- Range in size from less than 1/4 inch to nearly 2 inches (a few millimeters to 5 centimeters) in diameter
- Occur on nearly any part of your body, including your fingernails, but are found most often on your face, trunk and neck
Sometimes an epidermoid cyst has a central opening the remnant of a hair follicle from which the cyst originally formed that’s plugged by a tiny blackhead. You may be able to squeeze out a thick, cheesy material through this opening, but because of the risk of infection and scarring, it’s best to leave this to your dermatologist.
Milia tiny, deep-seated whiteheads that never seem to come to the surface of your skin are miniature epidermoid cysts. They’re especially common in older women and in men with significant sun damage on their cheeks and temples. They can also be caused or aggravated by long-term use of oil-based creams or cosmetics.
Symptoms of Sebaceous Cyst
The main symptom is usually a small, non-painful lump beneath the skin. The lump is usually found on the face, neck and trunk. It usually grows slowly and is not painful.
If the lump becomes infected or inflamed, other symptoms may include:
- Skin redness
- Tender or sore skin
- Warm skin in the affected area
- Grayish-white, cheesy, foul-smelling material that drains from the cyst
Signs and symptoms of infection, which can occasionally occur, include:
- A thick, yellow material draining from the cyst that may have a foul odor
- Redness, swelling and tenderness around the cyst
Causes of Sebaceous Cyst
The surface of your skin (epidermis) is made up of a thin, protective layer of cells that your body continuously sheds. Most epidermoid cysts form when these cells move deeper into your skin and multiply rather than slough off.
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.
Many people refer to epidermoid cysts as sebaceous cysts, but they’re different. True sebaceous cysts are less common. They arise from the glands that secrete oily matter that lubricates hair and skin (sebaceous glands).
A similar looking condition
Sometimes you may develop a small bump on your scalp that looks like an epidermoid cyst. These are almost always pilar or trichilemmal cysts, which usually have thicker walls than epidermoid cysts do and almost always move freely under your skin. The lining of this type of cyst differs slightly from that of an epidermoid cyst.
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.
Several factors can lead to this abnormal proliferation of cells, including:
- Damage to a hair follicle. Each hair grows from a follicle, a small pocket of modified skin in the dermis, the layer of skin just below the epidermis. Follicles damaged by injuries, such as abrasions or surgical wounds, can become blocked by surface cells.
- A ruptured sebaceous gland. Located just above the hair follicles, sebaceous glands produce sebum, the oil that lubricates your skin and coats each hair shaft. These glands are easily ruptured by inflammatory skin conditions, especially acne, making them a likely site for epidermoid cysts.
- Developmental defect. Epidermoid cysts can begin in a developing fetus when stem cells intended to form skin, hair or nails become trapped in cells forming other tissues.
- Heredity. Epidermoid cysts can develop in people with Gardner’s syndrome, a rare genetic disorder that causes growths in the colon, or basal cell nevus syndrome, an inherited disease that leads to several serious defects.
How are sebaceous cysts diagnosed?
Usually, a doctor can diagnose these cysts with a simple examination of the skin. In some cases, the doctor will perform a biopsy to rule out other skin growths.
How are sebaceous cysts treated?
In most cases, sebaceous cysts can be ignored as they usually are not dangerous. If a small cyst becomes inflamed, a doctor can inject it with a steroid drug to reduce swelling. A doctor may drain a cyst that is large, tender or inflamed. Larger cysts may need to be removed if they cause hair loss on the scalp or interfere with clothing.