A pilonidal cyst
defines a small mass under the skin and localized primarily in the crease of the buttocks, along the coccyx
. It essentially contains skin and hair and tends to become infected repeatedly. This is a completely benign cyst
but during its inflammatory period, it can trigger severe pain
. A pilonidal cyst can be removed by surgery if it is inflamed, painful, or too large, but removal does not guarantee that it will not return.