The Hair Loss Encyclopedia
non-cancerous lumps under skin filled with keratin
Epidermal cysts, also known as epidermoid cysts, are non-cancerous, small, round lumps beneath the skin. They form when skin cells multiply and create a sac filled with keratin, a protein found in skin, hair, and nails. These cysts are typically painless and slow-growing, but they can become inflamed or infected, causing discomfort.