Ovarian Endometriotic Cyst 

An ovarian endometrioma is a cyst that’s filled with the same fluid that’s in the lining of your uterus (endometrium). Sometimes called “chocolate cysts,” the fluid inside an ovarian endometrioma resembles chocolate syrup. Instead of being in your uterus, though, ovarian endometriomas form in your ovaries. Having an ovarian endometrioma is a sign that you have endometriosis, a condition that happens when endometrial-like tissue takes hold in places outside your uterus.