Sebaceous cysts are created when a small amount of sebum is retained under the skin and blocked by an overgrowth of surface skin. They are relatively uncommon and are often confused with epidermoid cysts (also known as infundibular cysts) and pilar cysts.
Sebaceous cysts are filled with a clear, oily liquid made by the sebaceous glands and are usually found on the face, neck and trunk of the body.
Epidermoid cysts usually affect young and middle-aged adults and contain keratin and pus. These can be formed after trauma or injury or from a hair follicle that has become inflamed.
Pilar cysts are subcutaneous keratin-filled cysts that originate from the outer hair root sheath. They can often be found in multiples on the scalp of middle-aged females.
While different in appearance and substance, all three cysts are treated the same way using diathermy with a few adaptations based on the position of the cyst.