SMAD4 and neoplasm: The fraction of MSI tumours has been reported to be higher in SCRC than that of solitary tumours (~15%), which our results also support.8,9,49 The mutation frequencies of known CRC genes in SCRCs resembled those seen in solitary tumours.50 Even genes whose mutation frequencies have been reported to differ in SCRC, such as BRAF, SMAD4, PIK3CA, and NRAS, showed no clear difference in our study.8,17