In this context, it is noteworthy that regions of tumours with patchy or subclonal MMR protein loss are known to have elevated frequencies of MSI [45] or somatic MMR gene mutations [46,47], and subclonal or weak MMR protein staining has recently been shown to account for much of the discordance between IHC and MSI assays [48,49]. The gene discussed is MRC1; the disease is neoplasm.