Family history as a major prerequisite for microsatellite instability screening in colorectal cancer is a poor selection tool.

Background: Deficient mismatch repair (MMR) leading to microsatellite instability (MSI) in tumors is thought to be present in over 15% of colorectal cancer (CRC) cases. Testing CRC for MSI has traditionally been recommended following the fulfillment of clinical criteria. However, the performance of clinical criteria, especially the family history, as a selection tool for MSI screening in CRC is questionable.

Microsatellite instability is highly prevalent in older patients with colorectal cancer.

Background: Clinical guidelines suggest screening of colorectal cancer (CRC) for microsatellite instability (MSI). However, microsatellite instability-high (MSI-H) CRC is not rare in older patients. This study aimed to investigate the prevalence of MSI-H CRC in an unselected population in an age-based manner.