MUC2 is a member of the mucin family of secreted glycoproteins that produces an insoluble mucous barrier in the gastrointestinal tract. MUC2 is implicated in the progression of ulcerative colitis, where it is downregulated. It has also been implicated in the formation or colorectal cancers. A MUC2 knockout model in mice demonstrated a propensity for colorectal cancer in its absence, as these mice frequently developed invasive colorectal adenocarcinomas. Staining is expected to be cytoplasmic within intestinal goblet cells and airway epithelium, and potentially in secretions, as well as within mucinous carcinomas of the colon, breast, pancreas, ovary, and stomach. References: Allen, 1998; Moehle, 2006; Betge, 2016; Velcich, 2002; Oncotarget 2017 8(42):71456; Am J Surg Path 2005 29(3):359