A pilonidal cyst is a blanket term for any type of skin infection near the tailbone. These are normally quite painful, generally occur in men, and normally happen in early adulthood. Although usually found near the tailbone, this painful condition can be found in several places, including the navel or the armpit. Development of the condition in a place other than the tailbone is exceedingly rare, however. It usually happens in young people, up to their thirties in age.