MRC1 and acinar cell carcinoma: Contemporary studies using state of the art technology usually reported MMR protein defects and MSI in about 0.5–3% of cancers, irrespective of the cancer type analyzed.14 Accordingly, the absence of detectable MMR protein loss in any of the 55 interpretable adenocarcinomas of the ampulla of Vater or 7 acinar cell carcinomas does not suggest absence of MSI in these tumor entities.