A case of unique endoscopic findings of intestinal endometriosis exposed to the mucosa: aggregation of papillary protruded bulges from the submucosal elevation of the rectum

Intestinal endometriosis exposed to the mucosa is relatively rare. Therefore, its endoscopic findings with pit pattern and magnifying endoscopy with narrow-band imaging and clinicopathological features of intestinal endometriosis exposed to the mucosa have not been well documented until now. A 44-year-old woman was suspected to have gastrointestinal bleeding by positive fecal occult blood test. Colonoscopy revealed a hemicircular submucosal tumor whose surface was covered with easy-bleeding papillary bulges in the rectum. Pit pattern analysis and magnifying endoscopy with narrow-band imaging revealed straight microvessels among the straight pits arranged in a radial manner, and the avascular area with no pit pattern of the top of the bulge. These findings were different from those of polyps or cancer. Biopsy specimens from the protruded lesions were diagnosed as rectal mucosal endometriosis by hematoxylin–eosin staining and immunohistochemical examination. Surgical resection was suggested to the patient, but the patient did not favor surgical treatment. After the diagnosis dienogest treatment started and successfully relieved her abdominal pain. Malignant transformation of the endometriotic lesion has not arisen to this date.