Ovarian chocolate cyst, also known as ovarian endometriosis cyst, is the most complicated disease in gynecological diseases, a lingering nightmare for sick women, and the most intractable benign tumor. It sticks everywhere and wanders around, and it is easy to relapse after treatment, and it is difficult to heal. The most common site of chocolate cyst is ovary. Because the cyst contains old dark brown menstrual blood, it is called chocolate cyst. Every time it passes, the cyst will be enlarged due to local congestion, which may cause the cyst to rupture. Chocolate cyst is a kind of pathological change of endometriosis. It is an ectopic pathological change caused by endometrial debris planted on the surface of ovary. Every menstrual period, there is local bleeding, which makes the ovary enlarged and forms a cyst containing old hematocele. This old blood is brown, sticky and like chocolate, so it is called "chocolate cyst".