An epidermal cyst is a freely movable nodule with essentially normal overlying skin. It is one of the most common benign skin tumors. The cyst wall is made of true epidermis (the most superficial part of the skin). The most common locations include the face, ears, neck, back and scalp. A central pore may be seen. The cyst contains a whitish cheese-like substance. This material is broken down keratin (a major component of skin). Epidermal cysts may arise when the hair follicle is clogged, such as in severe acne, or from a penetrating injury.
Trichilemmal cysts (wens) appear very similar to epidermal cysts, however, they mainly occur on the scalp and are usually multiple. The wall is thicker thus tends to be removed more easily in one solid piece. This contrasts to the epidermal cyst that often can rupture into pieces while removal is being performed. If any piece of the cyst is left behind, the cyst likely will recur. Trichilemmal and epidermal cyst can be removed if they become bothersome.
Milia are usually found on the face, most notably around the eyes. They are small firm whitish lesions. They usually arise for no apparent reason but several diseases and dermatologic treatments can trigger their development. They are also very common on the faces of newborns and infants. Adult patients may request the milia be treated for cosmetic purposes. The lesions are not treated in infants, as they will resolve on their own in a few weeks to months.
Cited from the American Osteopathic College of Dermatology