Endometriomas are pelvic masses or cysts that arise from the ovary. They are often blood filled and have a thick dark chocolate consistency, hence their name “chocolate cyst.” They are made up of abberent endometrial cells that bleed during the monthly cycle, as a result of hormone changes. These cysts are often seen in conjunction with surrounding endometriosis. If left untreated they can become quite large and engulf or overtake the ovary. Symptoms include pelvic pain, and painful periods. Surgery for removal is the treatment of choice.