GNAS codon 201 mutations are uncommon in intraductal papillary neoplasms of the bile duct.
Matthaei H, Wu J, Dal Molin M, Debeljak M, Lingohr P, Katabi N, Klimstra DS, Adsay NV, Eshleman JR, Schulick RD, Kinzler KW, Vogelstein B, Hruban RH, Maitra A. GNAS codon 201 mutations are uncommon in intraductal papillary neoplasms of the bile duct. HPB (Oxford). 2012 Oct; 14(10):677-83.