In sporadic colorectal tumours, germline mutations of MMR genes are rare in tumours that are MSI-high, but lack of expression of MLH1 has been found to be very common (up to 95%) in sporadic MSI+ tumours and is thought to be due to hypermethylation of the promoter region of MLH1 gene [111]. The gene discussed is MLH1; the disease is neoplasm.