Microsatellite instability is absent in liver and biliary mucosa of patients with primary sclerosing cholangitis

Microsatellite instability occurs in the colonic mucosa of patients with in flammatory bowel disease and may predispose the mucosa to neoplastic transf ormation. It is unknown whether microsatellite instability also plays a rol e in the neoplastic risk associated with primary sclerosing cholangitis. We examined 134 tissue samples from 21 patients with sclerosing cholangitis f or microsatellite instability at eight loci. Ail tissues were also stained immunohistochemically using an antibody to the proliferation marker Ki-67. Microsatellite instability did not occur in any samples from the intrahepat ic or extrahepatic biliary system, although one patient demonstrated instab ility in the colon. Ki-67 indices ranged from 0 to 2.5 in nondysplastic bil iary epithelium and from 1.5 to 29.4 in areas of dysplasia. The absence of microsatellite instability in sclerosing cholangitis suggests that the gene tic basis of neoplastic progression in chronic inflammatory disease of the bile ducts differs from that of intestinal cancers arising in the setting o f chronic inflammatory bowel disease and may relate to differences in the m icroenvironment in these two sites.