GI IMAGE IgG4-Related Disease of the Appendix Fadl H. Veerankutty 1 & Suhail Saleem 2 & Sidharth Chacko 1 & Vipin I. Sreekumar 1 & Prasad Krishnan 1 & Deepak Varma 1 & Prakash Kurumboor 1 Received: 25 October 2017 /Accepted: 7 November 2017 # 2017 The Society for Surgery of the Alimentary Tract Keywords Appendix . Mucocele . IgG4-related disease . Right iliac fossa mass Case A 57-year-old gentleman presented with dull aching pain in the right iliac fossa (RIF) and weight loss for last 4– 5 months. There was no history of fever, vomiting, an- orexia, gastrointestinal bleed, altered bowel habits, and respiratory or urinary symptoms. Past medical history was not significant except for diabetes. On clinical ex- amination, there was a tender firm mass in RIF. Laboratory investigations revealed the following: hemo- globin, 9.7 g/dL; total leukocyte count, 7.7 K/uL; CRP –145 mg/L; CEA –6.16 ng/ml; and normal renal and liver function tests. Abdominal CT showed a hugely dilated appendix with thickened walls. There was intraluminal fluid density with bubbles of gas and a fecalith inside. The rest of the abdominal organs appeared normal (Fig. 1a). Considering the high possi- bility of it being a malignant mucocele, we decided to proceed with laparoscopic right hemicolectomy. Intraoperatively, there was a 12 × 8-cm appendiceal tu- mor with adherent omentum. Surprisingly, histopathological examination of cut section of appendix demonstrated a lesion with patchy dense lymphoplasmacytic infiltration of submucosa with perivascular lymphoplasmacytic cuffing (Fig. 1b, c) and focal storiform pattern (cart wheel appearance) of fibrosis (Fig. 1d). Extensive areas of collagenization were also noted. Adjacent colon appeared histologically unremarkable. Pericolic lymph nodes showed only reactive changes. On immunohistochem- ical analysis (IHC), there was abundant infiltration of IgG4- positive plasma cells with high ratio of IgG4-positive to IgG- positive plasma cells per high-power field (IgG4/IgG= 100/ 240 = 41.66%) (Fig. 2a, b). Hence, though rare, a diagnosis of IgG4-related disease (IgG4-RD) of appendix was made. 1, 2 Patient is currently asymptomatic and has gained weight at 3 months of follow-up. Discussion IgG4-RD is an increasingly recognized immune-mediated condition affecting predominantly middle-aged and older men. The disease frequently presents both clinically and radiologically with features that mimic malignancy. Pancreas is the most common intra-abdominal organ af- fected, followed by the biliary tract. Involvement of the * Fadl H. Veerankutty fadl_05@yahoo.com 1 Department of GI and HPB Surgery, Aster Medcity, Cochin 682027, India 2 Department of Pathology, Aster Medcity, Cochin 682027, India J Gastrointest Surg https://doi.org/10.1007/s11605-017-3636-2