放大的卵巢切面示巧克力囊肿
子宫内膜移位症时血液流入卵巢导致巧克力囊肿的发生，因在卵巢中的陈旧血液被破坏形成含铁血黄素呈棕黑色而得名。
子宫内膜移位症：发生部位（模式图） | 镜下 | 移位于结肠（镜下） | 移位于子宫后浆膜下(大体) | 移位于子宫后浆膜下（肉眼放大） | 卵巢切面示巧克力囊肿 | 巧克力囊肿(中倍镜)
This is a section through an enlarnged 12 cm ovary to demonstrate a cystic cavity filled with old blood typical for endometriosis with formation of an endometriotic, or "chocolate", cyst. The hemorrhage from endometriosis into the ovary may give rise to a large "chocolate cyst" so named because the old blood in the cystic space formed by the hemorrhage is broken down to produce much hemosiderin and a brown to black color.