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 where 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 months or weeks before you notice the cyst.

Other causes of a sebaceous cyst may include:

• a misshapen or deformed duct
• damage to the cells during a surgery
• genetic conditions, such as Gardner’s syndrome or basal cell nevus syndrome

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:

• a diameter that is larger than five centimeters
• a 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 spot abnormalities
• ultrasounds, which identify the contents inside 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 is not because they are dangerous but rather for cosmetic reasons. Since most cysts are not harmful to your health, your doctor will allow you to pick the treatment option that works for you.

It is 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: completely removes a cyst but can leave a long scar
• minimal excision: causes minimal scarring but carries a risk that the cyst will return
• laser with punch biopsy excision: the laser is used to make a small hole to drain cyst contents and 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.