Retroperitoneal Endometriotic Cyst Mimicking a Tumor

Ectopic endometrial tissues are rarely observed on the serosal surfaces of bowel and laparotomy incisions, in the lungs, bones and in the urinary tract. Recto-sigmoid junction is the most common site of extra-genital endometriosis, with less frequent sites being the rectovaginal septum, small intestine, cecum and appendix. Endometriotic cyst in a retroperitoneal location mimicking a retroperitoneal tumor through the mesentery of sigmoid colon is an extremely rare presentation. Only few cases of retroperitoneal presentation of endometriotic cyst have been reported in the English literature. Retroperitoneal endometriotic cyst may mimic a retroperitoneal tumor in view of the location.