Rectal Polypoid Endometriosis Mimicking Malignant Rectal Tumor

Endometriosis is a disorder that presents as endometrial glands and stroma outside the uterine cavity and its musculature. It is a common gynecologic disease affecting approximately 15% of fertile women. However, polypoid endometriosis is rare. Our patient visited the hospital due to bowel habit changes and bloody stools. The colonoscopy revealed a large ulcerating polypoid mass in the rectum. Image studies including CT scan, MRI, and PET-CT suggested rectal cancer but the biopsy was negative for a malignancy. Finally, she was diagnosed with rectal polypoid endometriosis by a surgical rectal mass resection. We report a case of rectal polypoid endometriosis mimicking a rectal polypoid cancer. (Korean J Gastrointest Endosc 2007;34:156-160)