What is an epidermal inclusion cyst? What does it look like?

What is an epidermal inclusion cyst? What does it look like?

An epidermal inclusion cyst is the most common cutaneous cyst. Epidermal inclusion cysts are also known as epidermal cysts, epidermoid cysts, infundibular cysts and keratin cysts.

Epidermal inclusion cysts are sometimes referred to as “sebaceous cysts,” however this is a misnomer as this lesion does not involve the sebaceous gland. The term “sebaceous cyst” should only be used in association with steatocystoma multiplex.

An epidermal inclusion cyst typically appears as a slowly enlarging, mobile, dome-shaped lump, filled with keratin material and located just below the surface of the skin. They can range in size from 0.5 cm to several centimeters. Often times, there is a “punctum,” or small dark-colored opening on the surface of the epidermal inclusion cyst, which connects to the cyst located below skin’s surface. Through the opening, the keratin material may be drained out. This should only be done by a dermatologist or other healthcare provider.

Epidermal inclusion cysts are generally considered benign (non-cancerous), although there have been rare cases of malignancy arising within the cyst.