Cysts on the skin are harmless skin-colored bumps under your skin, usually on the face, neck and trunk, that are commonly known as epidermal cysts, epidermoid cysts, epidermal inclusion cysts, or improperly as "sebaceous cysts". These cysts form when the top layer of skin that normally sheds every few weeks, moves deeper into your skin and clogs the pore. With time, the layer becomes a living lining that secretes protein keratin, and dead cells accumulate, further clogging the pore. Sometimes cysts form when skin or hair follicle is injured. Sometimes they are visible as tiny blackheads plugging the opening of the cysts, and sometimes, the thick, smelly, yellow cheesy content drains from the cysts. They can occur in unusual number and locations like shoulders and arms instead of face and trunk in rare inherited conditions like Gardner Syndrome.
Epidermal cysts have three fates: they may remain stable, they may enlarge with time, or they may resolve spontaneous rupture and drainage, if the lining or sac of the cyst scars down. They are usually slow-growing and often painless, so they rarely cause problems or need treatments. However, larger cysts may be unsightly, painful, ruptured, infected, and occasionally cause physical disfigurement. Sometimes they get infected when patients manipulate or lance the cysts at home using non sterile technique or instruments. A foul smelling pus draining from the cyst, or severe redness or swelling around is usually a sign of infection and needs immediate attention.
Treatment options include surgical removal in which the entire cyst, including the lining, is surgically removed. The edges of skin are then sutured to close the gap left by the cyst. This is done in an office setting, under local anesthesia. Cysts can also be drained especially if fluctuant from infection and pus collection, causing severe pain. Antibiotics, bacterial cultures to confirm the identity of infection-causing bacteria, and confirmation of antibiotic activity against the bacteria may be needed. Unless the sac or lining of the cyst is entirely removed, the cysts may grow back. It is important to submit any collected cyst specimen and lining for pathological evaluation by a trained dermatopathologist to rule out worrisome mimickers of cysts like desmoplastic melanoma, cystic basal cell cancer, trichoblastic carcinoma.
Talk to your dermatologist if you develop any worrisome signs or symptoms so the bests treatment option can be presented to you.