Final answer:
Epidermal cysts arise from epidermal cells forming a keratin-filled sac, typically due to skin trauma or blockages, while dermoid cysts are complex growths containing various tissue types and usually develop from birth or during childhood, often deeper within the skin layers.
Step-by-step explanation:
The skin is composed of two main layers, the epidermis and the dermis. An epidermal cyst, also known as an epidermoid cyst, is a benign growth that occurs when epithelial cells form a sac and become filled with keratin. These cysts can occur on any part of the skin, originating in the epidermis. The cyst wall is made up of the same cells as the surface of the skin, and it is often found in areas with thicker epidermal layers. On the other hand, a dermoid cyst is a type of teratoma, which is a more complex growth that can contain a variety of tissues such as skin, hair, and sometimes even teeth, typically because they contain cell types from all three germ layers. These cysts are usually deeper and involve not just the epidermis but also the dermis layer, and are often present at birth or develop during childhood.
Both types of cysts are generally noncancerous, but an epidermal cyst is more likely to occur following trauma to the skin, such as a hair follicle becoming blocked. Dermoid cysts, due to their developmental nature, do not result from trauma and may be found in areas like the face, neck, or inside the body. They are sometimes even present on ovaries in women. While both can grow slowly and may not require immediate treatment, they can become infected and may need to be surgically removed, especially if they cause discomfort or cosmetic concerns.