Table 2 Revised Bethesda guidelines for colorectal cancers for microsatellite instability testing

Tumors from patients with colorectal cancer (CRC) should be tested for MSI in the following situations:

1. CRC diagnosed in a patient less than 50 years

2. Presence of synchronous, metachronous colorectal, or other Lynch syndrome (LS)-associated tumors, regardless of age

3. CRC with MSI-H phenotype diagnosed in a patient less than 60 years

4. CRC diagnosed in a patient with one or more first-degree relatives with an LS-associated tumor, with one of the cancers being diagnosed under the age of 50 years

5. CRC diagnosed in two or more first- or second-degree relatives with LS-associated tumors, regardless of age