Microsatellite Instability Is Absent in Liver and Biliary Mucosa of Patients with Primary Sclerosing Cholangitis

Microsatellite instability occurs in the colonicmucosa of patients with inflammatory bowel disease andmay predispose the mucosa to neoplastic transformation.It is unknown wheThe r microsatellite instability also plays a role in the neoplastic riskassociated with primary sclerosing cholangitis. Weexamined 134 tissue samples from 21 patients withsclerosing cholangitis for microsatellite instability ateight loci. All tissues were also stainedimmunohistochemically using an antibody to theproliferation marker Ki-67. Microsatellite instabilitydid not occur in any samples from the intrahepatic orextrahepatic biliary system, although one patientdemonstrated instability in the colon. Ki-67 indicesranged from 0 to 2.5 in nondysplastic biliary epitheliumand from 1.5 to 29.4 in areas of dysplasia. The absence of microsatellite instability in sclerosingcholangitis suggests that the genetic basis ofneoplastic progression in chronic inflammatory diseaseof the bile ducts differs from that of intestinalcancers arising in the setting of chronic inflammatorybowel disease and may relate to differences in themicroenvironment in these two sites.