When IgG4-related sclerosing disease clinically mimicks a rectal adenocarcinoma: a case report.

IgG4 related sclerosing disease is a fairly newly recognised fibro-inflammatory condition that was only initially observed in autoimmune pancreatitis. However, recent observations have shown similar findings described in virtually every organ system. We report a case of suspected IgG4 related disease mimicking an extensive rectal adenocarcinoma. A 54-year-old man presented with a five month history of lower abdominal pain associated with a 4 kg loss of weight. A CT colonography showed an annular mass projecting into the rectum with luminal narrowing. The sigmoid colon showed gross thickening, diverticula, fibrosis and stranding in the adjacent fat. The roof of the bladder was also grossly thickened. A pelvic exenteration with ileal conduit and ileostomy was performed. The sections of colonic mucosa showed multiple diverticula with ulceration, storiform fibrosis and abscess formation as well as a dense inflammatory cell infiltrate comprised of plasma cells and lymphocytes. These changes extended into the bladder and prostatic tissue. Immunohistochemical stains for IgG4 showed areas of increased plasma cells staining suggesting a relationship to IgG4 sclerosing disease. Despite IgG4 being fairly new, IgG4 related sclerosing disease should be considered as a possible clinical and radiological mimic of malignancy to avoid unnecessary resections.Copyright © 2018