The picture shown above shows a huge ovary adjacent to the uterus. The dark brown color earns it the name chocolate cyst. This is seen most often in a condition called endometriosis in which the uterine endometrial tissue is found in ectopic locations. They could be the ovaries, the rectouterine pouch and even in rare cases, surgical scars and lungs. The tissues bleed cyclically with each menstrual cycle and cause scarring. Chronic bleeds into the ovary result in the formation of these chocolate cysts, also referred to as endometriomas. Image credits- http://www.operationalmedicine.org/ed2/Video/chocolate_cyst_of_the_ovary_vide.htm