Epidermoid cyst

What it means

Nontender, round and firm, but slightly compressible, intradermal or subcutaneous cyst measuring 0.5-5 cm in diameter. Epidermal cysts are intradermal or subcutaneous tumors, grow slowly and occur on the face, neck, back and scrotum. They usually appear at or around puberty, and as a rule an affected individual has one solitary or a few cysts. A central, dark comedone opening (punctum) may be present.

A cyst is a cavity containing liquid, semisolid, or solid material. An epidermoid cyst is a benign cyst that develops out of ectodermal tissue and consists of a thin layer of squamous epithelium. An epidermal cyst may or may not be painful or release pus, and are usually noticed as a bump on the skin. Epidermal cysts and trichilemmal cysts are clinically indistinguishable. The wall of the epidermal cyst conserves the epidermal layers, but the wall of the trichilemmal cysts, which arise from the external root sheath, shows palisading of unlayered epithelial cells. Homogeneous horny material that is further degraded to fat and cholesterol forms within both types of cysts.

Rare diseases that can present with this9

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category

Also called: Central punctum opening in cyst · Epidermal cyst · Epidermal inclusion cyst · Epidermoid cysts · Infundibular cyst · Keratin cyst · Sebaceous cyst