Different amounts of K-ras mutant epithelial cells in pancreatic carcinomaand mass-forming pancreatitis

Clinically, differential diagnosis of pancreatic carcinoma (PC) and so-call ed "mass-forming pancreatitis (MFP)" is difficult. We analyzed the amount, ductal level, and K-ras mutation of ductal hyperplasia and intraductal carc inoma in surgically resected cases of MFP (n = 18) and PC (n = 16). DNAs ex tracted from microdissected epithelial foci were analyzed for K-ras codon 1 2 mutation by nested polymerase chain reaction and restriction fragment len gth polymorphism. The histology of MFP showed severe destruction of exocrin e tissue and pancreatic stones and/or protein plugs (72%, 13 of 18 cases) i n mostly peripheral ducts. The average basal membrane lengths of nonpapilla ry and papillary hyperplasia in cases of carcinoma were about 4 and 15 time s more than those of MFP, respectively. The frequency of K-ras mutation in hyperplastic foci increased from nonpapillary [six (27%) of 22] to papillar y foci [16 (64%) of 25] in K-ras mutant PCs, but there was no difference be tween nonpapillary [one (6%) of 18] and papillary foci (none of 19) in K-ra s wild-type PCs, and also between nonpapillary (none of 24) and papillary f oci [one (7%) of 14] in MFPs.