A Pseudotumor. No. It’s a Granulomatous Diverticulitis in Disguise A Pseudotumor? No! It’s a Granulomatous Diverticulitis in Disguise! Hassan Al Moussawi MD, Fady G. Haddad MD, Sandy El Bitar MD, Mayurathan Kesavan MD, Liliane Deeb MD Staten Island University Hospital/Northwell Health, Staten Island, New York 42 * 60 It usually affects the left colon excluding cecum and ascending colon. In this setting, caution should be exercised to avoid an inappropriate diagnosis of Crohn's disease. Introduction  Discussion Diverticular Disease (DD) encompasses a broad scope of manifestations including chronic colitis. Diverticular Disease-Associated Colitis (DAC) is a distinct entity that can occasionally exhibit granulomatous inflammation. Although granulomatous colitis associated with diverticulosis has been rarely described, our patient is the 1st case affecting the right colon to be reported in the English literature. He presented with a hypermetabolic tumor-like mass abutting the right colon that was further identified as granulomatous reaction secondary to DAC . DD is a leading cause of hospitalizations in developed countries affecting 30-50% of individuals older than 60 years. DAC describes the occurrence of mucosal inflammation in a colon segment affected with DD with relative sparing of the rectum and proximal colon. Its prevalence is suggested around 1.3-3.8%. Pathogenesis is multifactorial with multiple reports noting clinicopathological overlap between DAC and IBD especially in patients with granulomatous colitis as in our case.   Fig 2: PET showing increased colonic mass metabolic activity.           On PET scan the mass exhibited increased metabolic activity suspicious for tumor (Fig2). CT guided biopsy revealed inflammatory cells. A diagnostic laparoscopy with fresh frozen section was inconclusive for malignancy, followed by a robotic assisted right hemicolectomy enbloc with the mass. Pathology showed diverticulitis with localized suppurative granulomatous inflammation (Fig3). The non-caseating granulomas consisted of epithelioid histiocytes with abundant eosinophic cytoplasm and eccentric nuclei (Fig4,A). Immunostains were positive for CD68 (Fig4,B) and Vimentin (Fig4,C), negative for Pancytokeratin (Fig4,D), eliminating the possibility of a carcinoma or a sarcoma. Fig 4 (A,B,C,D): Microscopic pathology and immunostains Fig 1: Abd CT (coronal) showing ascending colon mass. In this setting, caution should be exercised to avoid an inappropriate diagnosis of Crohn's disease. Recurrence rates and long term outcomes of DAC are not well defined and could range from a benign course to an overt IBD. Case Presentation A 77 y.o. man with Diabetes Mellitus and Hypertension presented with right lower quadrant abdominal pain that started few weeks prior. The pain was ill defined and had no radiation. Physical examination revealed a palpable right lower quadrant mass. The patient underwent a contrast Abdominal Computed Tomography (CT) scan revealing a 5.5cm irregular soft tissue mass abutting the ascending colon medially (Fig1). Colonoscopy revealed diverticulosis in sigmoid and ascending colon.  Conclusion We report the first case of Granulomatous Diverticulitis affecting the right colon. This entity is not well characterized. View its similarities with colonic malignancies and IBD, more studies are needed in order to further describe its pathophysiology and ouctomes. Fig 3: Gross pathology of Granulomatous diverticulitis.