A cyst arising from deep implanted epidermal cells.
Dermoid cysts arise from epidermal cells, which have been implanted into the dermis either during embry-onic development or following trauma. They are lined with squamous epithelium and contain sebum, cells and occasionally hair.
Cysts present as soft rubbery swellings deep to the skin. There may be fixation to the deep tissues.
· Congenital dermoid cysts are found at sites of embryonic fusion. The commonest congenital dermoid cyst occurs at the junction between the frontal bone and the maxilla at the lateral border of the orbit (external angular dermoid).
· Implantation cysts occur following traumatic implantation of epidermal cells. The surrounding skin and subcutaneous tissue may be erythematous and swollen.
Dermoid cysts are surgically removed. Congenital dermoid cysts require general anaesthesia due to the deep extension.