Earlier IHC studies described MMR deficiency in 0–22%.22,23 Highest rates were reported in two TMA studies describing MMR deficiency in 15% of 265 and in 22% of 109 resected pancreatic cancers.22,37 Immunostaining issues in case of unevenly fixed tissues, as seen in our study, may serve as an explanation for such high frequencies of undetectable MMR protein in cancers. The gene discussed is MRC1; the disease is mismatch repair cancer syndrome 1.