Also known as a pilonidal cyst, the condition forms when a sac of tissue fills with air or fluid in the crease of your buttocks. Pilonidal cyst, doctors say, is mostly caused by a skin infection.
Medically reviewed by Susan Bard, MD Key Takeaways A pilonidal cyst is a painful lump located at the base of the spine at the top of the buttocks.Symptoms can include a painful lump, discharge, and ...