S2097 Pseudomyxoma Peritonei Presenting with Extrinsic Compression on Esophagogastroduodenoscopy and Colonoscopy

Abstract

INTRODUCTION: Pseudomyxoma peritonei (PMP) is a rare disease characterized by mucinous ascites, classically originating from a ruptured low-grade appendiceal mucocele. We present a case of PMP identified because of signs of extrinsic compression on esophagogastroduodenoscopy (EGD) and colonoscopy. CASE DESCRIPTION/METHODS: A 66-year-old male presented for screening colonoscopy and EGD. His medical history was significant for renal calculi and recurrent acid reflux resistant to medical therapy. He denied weight gain or abdominal distension. A colonoscopy performed six years prior identified a single 3 mm tubular adenoma, diverticulosis, and internal hemorrhoids. Colonoscopy revealed sigmoid diverticulosis, a benign stricture in the recto-sigmoid colon, and a large, extrinsic-appearing mass in the descending colon (Figure 1). EGD revealed LA Grade C reflux esophagitis, a hiatal hernia, gastritis, one large non-bleeding duodenal ulcer with a clean ulcer base, and possible extrinsic compression in the gastric body (Figure 2). A CT Abdomen/Pelvis with contrast was obtained to further characterize this apparent extrinsic compression, which revealed diffuse low-density masses and ascites distending the peritoneal cavity with scalloped appearance of the liver and spleen. He was referred to surgical oncology and underwent a diagnostic laparoscopy with peritoneal biopsies that revealed extensive mucin and fibrin deposits, consistent with PMP. He underwent cytoreduction, right hemicolectomy, and hyperthermic intraperitoneal chemotherapy (HIPEC). Surgical pathology showed low grade mucinous carcinoma peritonei and the appendix showed a low-grade mucinous neoplasm. Repeat CT Abdomen/Pelvis with contrast revealed significantly improved peritoneal carcinomatosis and multiloculated, multiseptated, low attenuation masses throughout the abdomen. CEA was 58.3 at five months post-operative from 159.6 preoperatively. Seven months post-operatively the patient was doing well without findings concerning for recurrent disease. DISCUSSION: The incidence of PMP is estimated to be 1-3 per million per year. The growth of appendiceal mucinous tumors is indolent, and they are frequently diagnosed incidentally during evaluation for other conditions. They are classically identified on colonoscopy as an abnormal appearing appendiceal orifice (“volcano sign”) atop a “mound” of normal-appearing mucosa. This case highlights the importance of considering extraluminal etiologies for unexpected findings on endoscopy.Figure 1.: Extrinsic-appearing mass in the descending colon.Figure 2.: Possible gastric mass or extrinsic compression in the gastric body.Figure 3.: CT Abdomen/Pelvis with oral and IV contrast showing diffuse low-density masses and ascites, distending the peritoneal cavity with scalloped appearance of the liver.