Lack of mucin MUC5AC field change expression associated with tubulovillousand villous colorectal adenomas

Background-MUC5AC is a secreted mucin aberrantly expressed by polypoid colo rectal adenomas. It has been hypothesised that the "normal" surrounding col orectal mucosa expresses MUC5AC as a field change phenomenon that can be us ed to predict adenoma recurrence following resection. Aim-To determine if there is a field change of de novo MUC5AC expression in histologically normal rectal mucosa adjacent to villous and tubulovillous adenomas, and thus whether MUC5AC expression can be used as a marker of ear ly tumour recurrence. Methods-In a prospective cohort study paired mucosal biopsies of adenomatou s and macroscopically "normal'' mucosa were obtained from 11 patients with \villous and 11 patients with tubulovillous adenomas who underwent primary resection for purpose of cure. The tissues were studied to determine MUC5AC gene expression by immunohistochemistry and in situ hybridisation. Patient s were followed up by flexible sigmoidoscopy to detect the presence of earl y local recurrence. Results-10 villous adenomas showed mature MUC5AC glycoprotein and all 11 ex pressed MUC5AC mRNA. Five tubuolo-villous adenomas showed mature MUC5AC gly coprotein and 10 expressed MUC5AC mRNA, Neoexpression of the MUC5AC mucin g ene was not detected in any of the mucosal biopsies taken adjacent to eithe r villous or tubulovillous adenomas, even in three patients with early, loc ally recurrent disease. Conclusions-Aberrant MUC5AC gene expression is not a "field change" in the colorectal mucosa in patients with rectal adenomas and therefore cannot be used to predict local recurrence of villous and tubulovillous adenomas.