Sebaceous cysts are common noncancerous cysts of the skin. Cysts are abnormalities in the body that may contain liquid or semiliquid material.

Sebaceous cysts are mostly found on the face, neck, or torso. They grow slowly and aren’t life-threatening, but they may become uncomfortable if they go unchecked.

Doctors usually diagnose a cyst with only a physical examination and a medical history.

In some cases, a cyst will be examined more thoroughly for signs of cancer.

Sebaceous cysts form out of your sebaceous gland. The sebaceous gland produces the oil (called sebum) that coats your hair and skin.

Cysts can develop if the gland or its duct (the passage from which the oil is able to leave) becomes damaged or blocked. This usually occurs due to a trauma to the area.

The trauma may be a scratch, a surgical wound, or a skin condition, such as acne. Sebaceous cysts grow slowly, so the trauma may have occurred weeks or months before you notice the cyst.

Other causes of a sebaceous cyst may include:

Small cysts are typically not painful. Large cysts can range from uncomfortable to considerably painful. Large cysts on the face and neck may cause pressure and pain.

This type of cyst is typically filled with white flakes of keratin, which is also a key element that makes up your skin and nails. Most cysts are soft to the touch.

Areas on the body where cysts are usually found include:

  • scalp
  • face
  • neck
  • back

A sebaceous cyst is considered unusual — and possibly cancerous — if it has the following characteristics:

  • diameter that’s larger than five centimeters
  • fast rate of reoccurrence after being removed
  • signs of infection, such as redness, pain, or pus drainage

Doctors often diagnose a sebaceous cyst after a simple physical examination. If your cyst is unusual, your doctor may order additional tests to rule out possible cancers. You may also need these tests if you wish to have the cyst surgically removed.

Common tests used for a sebaceous cyst include:

  • CT scans, which help your doctor find the best route for surgery and to spot abnormalities
  • ultrasounds, which identify the contents of the cyst
  • punch biopsy, which involves removal of a small amount of tissue from the cyst to be examined in a laboratory for signs of cancer

Your doctor can treat a cyst by draining it or by surgically removing it. Normally, cysts are removed. This isn’t because they’re dangerous but rather for cosmetic reasons.

Since most cysts aren’t harmful to your health, your doctor will allow you to choose the treatment option that works for you.

It’s important to remember that without surgical removal, your cyst will usually come back. The best treatment is to ensure complete removal through surgery. Some people do decide against surgery, however, because it can cause scarring.

Your doctor may use one of the following methods to remove your cyst:

  • Conventional wide excision, which completely removes a cyst but can leave a long scar.
  • Minimal excision, which causes minimal scarring but carries a risk that the cyst will return.
  • Laser with punch biopsy excision, which uses a laser to make a small hole to drain the cyst of its contents (the outer walls of the cyst are removed about a month later).

After your cyst is removed, your doctor may give you an antibiotic ointment to prevent infection. You should use this until the healing process is complete. You may also be given a scar cream to reduce the appearance of any surgical scars.

Sebaceous cysts are generally not cancerous. Cysts left untreated can become very large and may eventually require surgical removal if they become uncomfortable.

If you have a complete surgical removal, the cyst will most likely not return in the future.

In rare cases, the removal site may become infected. Contact your doctor if your skin shows any signs of infection such as redness and pain or if you develop a fever. Most infections will go away with antibiotics, but some can be deadly if untreated.