What is epidermoid cyst?

Epidermoid cyst is a benign tumor of the subcutaneous tissue. It represents an increased accumulation of sebum and skin cells. Epidermoid cysts are mainly found on the head, face, neck, but also on other parts of the body.

Cause of occurrence?

The most common cause is the blockage of sebaceous gland secretion, but it can also be due to injury or infection of the skin.

Sebaceal cyst is a type of epidermoid cyst that is formed as a collection of keratin material. Sebum, which otherwise plays a role in skin protection, secretes sebaceous glands in subcutaneous tissue. Lipids, cholesterol crystals and skin cells accumulate and a squamous epithelium-lined node forms. It may also be due to genetic predisposition.

Clinically, an epidermoid cyst is a hard knot in the skin. However, in the breast, the lesion often grows deep inside the subcutaneous tissue of the breast and is located between the adipose tissue and the mammary gland. This makes clinical diagnosis difficult. On ultrasonography, it is seen as a solid, restricted and complex mass.

Epidermoid cyst becomes painful when inflamed, or when bacteria penetrate into it (eg, when a patient tries to squeeze a knot). Dermatologists advise that the knot should not be touched or pressed to prevent infection. If they are more than 5 cm in diameter, they are called giant epidermoid cysts, which rarely occur in the breast.

The Epidermoid cyst can be completely excised through a small incision in the skin under local anesthesia.


Treatment of an uncomplicated epidermoid cyst involves complete excision along with the capsule.

Malignant transformation of the epidermoid cyst wall occurs very rarely (0.045%). Therefore, for definitive histopathologic diagnosis, excision of all epidermoid cysts in the breast is usually recommended, thus excluding the possibility of a malignant lesion with seemingly benign features, that is, preventing potential complications such as infection and malignant transformation.