Histopathological and clinical differences between tumours with a mutation of a MMR gene and tumours with hypermethylation of the MLH1 promoter as a cause of dMMR have been described (Benatti et al, 2005; Jass, 2007), and therefore it seems reasonable to distinguish between these two types of dMMR tumours regarding response to therapy and survival (Poynter et al, 2008). The gene discussed is MRC1; the disease is neoplasm.