Ovarian cysts are fluid filled sacs inside the ovary. When the follicles (sacs) in the ovaries do not rupture, they form small cysts called simple cysts. Dermoid cysts & chocolate cysts are other types of cysts. Large or pathological cysts can occur in about 5% of women during their reproductive years. Ovarian cysts are common, frequently asymptomatic and often resolve spontaneously.