1498 A Rare Case of an Atypical Mass Involving the Sigmoid Colon

INTRODUCTION: The etiology of colonic masses is broad including benign polyps, primary adenocarcinoma, metastases, and diverticular mass. Presentation may be similar; therefore, the differentiation generally involves biopsy for histological evaluation and appropriate diagnosis. CASE DESCRIPTION/METHODS: A 34-year-old female presented with hematochezia and constipation. Her past medical history was significant for tubo-ovarian ovarian abscesses (TOAs), endometriosis fibroids and schwannoma of the paraspinal area. She reported new onset red blood per rectum, worsening constipation, and pelvic discomfort. Family history was notable for esophageal and colorectal cancer. She subsequently underwent colonoscopy which demonstrated a 3-4 cm nodular, polypoid fungating mass in the distal sigmoid colon located at 20-25 cm from the anal verge (Figure 1). Biopsies were obtained and the site was tattooed. A subsequent MRI of the abdomen and pelvis showed a heterogeneous inflammatory soft tissue encasing the ovaries and tethering the rectosigmoid colon (Figure 2). Additionally, there was a enhancing soft tissue mass invading the inferior wall of the distal sigmoid colon with an intraluminal component. The MRI findings were felt to be consistent with invasive endometriosis. Histological examination of the sigmoid mass showed colonic mucosa with polypoid endometriosis without evidence of malignancy (Figure 3). Cells showed positive immunohistochemical staining consistent with endometriosis. Surgical resection was recommended. DISCUSSION: This case demonstrates the importance of having a high suspicion of endometriosis involving the bowel in reproductive age women presenting with abdominal pain, dysmenorrhea, dyspareunia, and dyschezia. Endometriosis is a condition involving the implantation of endometrial stroma and glands at extra-uterine sites. Endometriosis tends to involve bowel serosa. It rarely encompasses full thickness of the bowel wall. The latter represents invasive endometriosis. Many patients are incorrectly diagnosed given their presentation. This disease increases risk of gastrointestinal tumors, primarily adenocarcinoma. Therefore, prompt recognition and treatment with hormonal therapy or surgical excision is important for symptom relief, increase in fertility, and later complications such as bowel stenosis, hydronephrosis, and malignant transformation.