Dr. Schwark on Microsatellite Instability and Lynch Syndrome

Alicia Latham Schwark, MD, medical genetics fellow, Memorial Sloan Kettering Cancer Center, discusses a study exploring microsatellite instability (MSI) and how it relates to Lynch syndrome across all tumor types. The findings were presented at the 2018 ASCO Annual Meeting.

Results showed that MSI-high (MSI-H) and DNA mismatch-repair deficient (dMMR) tumors are predictive of Lynch syndrome across all tumor types, suggesting a more heterogeneous spectrum of Lynch syndrome-associated cancers than previously suspected. Of 15,045 analyzed tumors spanning >50 cancers, 50% (33/66) of patients with Lynch syndrome had MSI-H tumors less commonly or not previously associated with Lynch syndrome.

Schwark adds that nearly 40% of patients with Lynch syndrome who have MSI-H non-colorectal or non-endometrial tumors did not meet clinical criteria for genetic testing. This suggests that these types of tumors, regardless of cancer type, should prompt Lynch syndrome testing.

Lynch syndrome is usually hereditary, with some rare cases of de novo mutations. Because of its gene type, Schwark says that when Lynch syndrome is not associated with cancer, it is often hard to detect.