An epidermoid cyst is an epitheliumlined cavity within the dermis filled with oily or fatty semisolid material.
Epidermoid cysts are common in the hair-bearing areas and are thought to arise from the blockage of a hair follicle. The commonest scalp cysts are pilar cysts, which may be inherited.
Patients present with a lump in the skin, so the skin cannot be moved over it. A characteristic surface punctum is often visible. If there is a superimposed infection the lump may become red, hot and tender.
Uninfected cysts are excised under local anaesthesia, if required using an elliptical incision.
Infected cysts are first incised and drained. Excision is performed if still necessary once the infection has been treated.