Mucin-6 (MUC6, oligomeric mucus/gel-forming) is a high-molecular weight secreted glycoprotein that forms a mucous barrier to protect luminal epithelium. It is expressed in the epithelium of the stomach, colon crypt, gallbladder, pancreatic ducts, seminal vesicle, and endocervix. It is also positive in some gastric carcinomas and mucinous carcinomas of the breast. References: Gastroent 1995 109:723; Histopath 2003 42(1):26; Cancer 2001 92(6):1427