Epidermoid

Epidermoid, a tumor-like formation representing a cystic cavity filled with a pasty mass of desquamated and softened epithelium; the wall of E. consists either of all layers of the skin or only of the epidermis. If the wall contains skin glands, it is then called a dermoid or dermoid cyst (see Dermoid). E. forms due to congenital or traumatic displacement of the skin. To distinguish E. from simple atheromas, they are also called dermoidal or epidermoidal atheromas. In the contents of the cyst, epithelium, fat droplets, detritus, often cholesterol, and frequently hairs are found. Initially, this content has a dense consistency, but later it becomes softened. Traumatic E., reaching the size of a small nut and occurring especially frequently on the back of the hand, particularly on the thumb, form by the implantation of skin or only its epithelium into the wound area; when only epithelium is implanted, epithelial pearls form.