Many people often call any small, painless lump under the skin "sebaceous cysts." But those are most often "epidermoid cysts." Sebaceous cysts are much less common and affect the sebaceous glands, the oil glands in the skin.
Epidermoid cysts can be made up of a protein called keratin and fat. They usually appear on the face, neck, or upper body, especially the chest and shoulders. They erupt for many reasons, most often because of acne or mild skin injuries. (When they are formed because of swelling around hair follicles, they are called pilar cysts.) Epidermoid cysts are usually small, from a few millimeters to about 5 centimeters across, and they grow slowly. They are more common in men than in women.
Actinic keratoses commonly appear in areas of chronic sun exposure, such as the face and dorsa of the hands. Actinic cheilitis is a related condition that usually appears on the lower lips. These conditions represent early epithelial transformation that may eventually evolve into invasive SCC.
Actinic keratosis is a noninvasive lesion. The progression rate is extremely low. In a prospective study, the progression rate to SCC was less than 1 in 1,000 per year, calling into question the cost effectiveness...
The cyst itself usually doesn't hurt, but it can become tender, sore, and red if it gets infected. If it pops, the cyst might ooze and smell bad.
Is it dangerous?
No. Epidermoid cysts are harmless and are almost never linked with cancer. If you're worried that it will grow into something more dangerous, check with your doctor to make sure it's not another type of skin problem.
Do I have to have it removed?
Not always. Sometimes smaller epidermoid cysts go away on their own, or can be treated with warm compresses. Even if a cyst gets infected, a doctor (usually a dermatologist) can sometimes treat it by injecting it with steroids. But if a cyst bothers you for any reason, you can see a doctor to have it removed.
How is an epidermoid cyst removed?
Your doctor may use antibiotics to reduce swelling. Then, after the swelling has eased, he can remove it.
Getting an epidermoid cyst removed is simple. Your doctor will probably numb your skin with local anesthesia, then make a very small cut in the surface of the cyst. He applies firm pressure to squeeze out all of the contents of the cyst. Be forewarned: Some of that bad-smelling pus inside the cyst may splatter around as it’s draining.
After the doctor is finished, he will close the cut with a small stitch, and later you will probably take antibiotics to fight any infection. If any of the contents are left inside the cyst, it can grow back again.
If that happens, the doctor may suggest you have another surgery.
Can I pop an epidermoid cyst myself?
You might be tempted to try to pop and drain an epidermoid cyst on your own, but this isn't a good idea. First, if the cyst is infected, the infection could spread if the cyst ruptures and drains unsafely. Second, if any of the cyst’s sac is left behind, it could grow back. If the cyst doesn't bother you, it’s fine to leave it alone. If it seems to be infected, is uncomfortable, or you don't like the way it looks, it’s best to have it checked by a doctor.