Microsatellite instability and p53 expression in gallbladder carcinomas.

We studied the MSI (microsatellite instability) status and p53 expression in a series of 71 gallbladder cancers (GCs) of different histologic type. All neoplasms were examined combining a microsatellite analysis at mononucleotide locus BAT-26 and an immunohistochemical study for hMSH2, hMLH1, and p53 proteins and markers of gastric and intestinal differentiation. All the 71 GCs were MSS (microsatellite stable). The p53 protein was found in 100% of undifferentiated GCs, 67% of conventional gallbladder adenocarcinomas, 50% of mucinous adenocarcinomas, and 20% GCs with squamous differentiation. All 71 MSS tumors showed presence of immunohistochemical expression of both hMLH1 and hMSH2 gene products. We concluded that microsatellite instability does not play a role in the developing of GC while p53 seems to be the most important alteration found in a large proportion of these cancers, with the only exception of mucinous and squamous gallbladder carcinomas.