Surgery for developmental cysts such as dermoid cysts, soft tissue lumps, and pigmented skin lesions may require procedures and are usually straightforward and performed as day-case surgery. Scar revision is usually performed after at least 18 months has elapsed to allow tissues to mature and heal. Depending on the extent of scarring or the size of a skin lesion more than one episode of surgery may be needed. A process called tissue expansion may be required in some cases if scarring or pigment covers a large area. This involves inserting a balloon expander to stretch the tissue with a series of expansion episodes before it is removed and the newly expanded skin can be re positioned.