In the present case, we identified a heterozygous variant in MSH3. Although it was expected to be silent, we tried to annotate the variant; in the tissue immunostaining, the expression of MSH3 was the same in the normal mucosa, adenomas, and carcinomas, suggesting that the MSH3 variant in our case was unlikely to have contributed to the development of polyposis or carcinogenesis. This evidence concerns the gene MSH3 and adenoma.