S2224 An Unusual Case of Hematochezia Secondary to Isolated Recto-Sigmoid Endometriosis Mimicking a Tumor

INTRODUCTION: Endometriosis, is defined as presence of endometrial glands and stroma outside of uterus, involving ovaries and pelvic peritoneum commonly. We are describing a rare case of isolated rectosigmoid endometriosis without any involvement of other pelvic structures presenting as rectal bleeding, and mimicking a tumor. CASE DESCRIPTION/METHODS: A 38-Yr-Old African American female, with no significant past medical history, was seen with complaints of episodic bright rectal bleeding, abdominal pain, nausea and vomiting for a week. She denied any anticoagulants, or NSAID use, weight loss, or family history of colorectal cancer. Examination showed mild tenderness in left lower quadrant. Labs: WBC 4600, HgB 9.1g/dL, HCT 28.3, Platelets 294000, MCV 72. Her baseline HgB was 10-11 a year ago. CMP, and lactic acid level were normal. A CT scan of abdomen and pelvis was normal except a small ovarian cyst, and tiny uterine fibroids. Colonoscopy showed a large, partially obstructing, friable, ulcerated, polypod mass at the rectosigmoid junction. The lesion could not be lifted for proper assessment, or mucosal resection. An endoscopic ultrasound showed invasion of perirectal fat (T3), without any surrounding lymph node enlargement. CEA was normal at 0.67 ng/mL. Pathology showed positive immunohistochemical stains for ER/PR, PAX8, CD10, CDX2, CK20, highlighting endometrial glands and stroma in a background of normal colonic mucosa, confirming the diagnosis of endometriosis. A repeat sigmoidoscopy with biopsy also showed similar findings. An MRI of pelvis showed mild asymmetric thickening of rectum , multiple small uterine fibroids without any soft tissue involvement in pelvis. She was given management options including hysterectomy with bilateral salpingo-oophorectomy with excision of colonic endometriosis. However, patient was concerned about fecundity and wanted to give a trial of medical therapy. She was started on Norethindrone acetate , and followed in gynecology clinic regularly with a plan for surgery in the future. DISCUSSION: Isolated bowel endometriosis is very rare and the clinical presentation, endoscopy, and imaging findings are variable posing a diagnostic challenge. Our patient presented with sudden onset of abdominal pain, and bleeding raising a concern for ischemic colitis. Colonoscopy findings were suspicious for a malignancy. The diagnosis was only possible with high degree of suspicion and thorough immunohistochemical staining.Figure 1.: 1. Normal colonic mucosa with endometrial glands and stroma.Figure 2.: 2. CD 10 stain: Positive endometrial stroma.Figure 3.: 3. Rectosigmoid mass.