Since colorectal tumors characterized by MSI and EMAST types of instability are distinct from MSS/EMAST-S tumors in many molecular aspects, we considered that their miRNA expression patterns could be affected by MLH1 methylation, a higher frequency of BRAF mutations, MSH3 dysfunction, and lower frequencies of APC, KRAS, and TP53 mutations. The gene discussed is KRAS; the disease is colorectal neoplasm.