An epidermoid cyst (often colloquially referred to as a sebaceous cyst) is a common, non-cancerous slow-growing sac beneath the skin containing keratin—a soft, yellowish protein that makes up hair, nails, and skin. While usually harmless, these cysts can become inflamed, infected, or aesthetically inconvenient. A professional epidermoid cyst extraction is a minor, out-patient dermatological or surgical procedure designed to clear the contents and—most importantly—completely remove the surrounding cyst capsule (sac) to prevent recurrence.