Douglas K. Rex, MD reviewing Sussman DA et al. Clin Gastroenterol Hepatol 2016 Apr 1.

Prevalence was similar across groups, supporting universal screening for MSI.

Microsatellite instability (MSI) is found in nearly all Lynch syndrome colorectal cancers and in about half of serrated pathway cancers. Because serrated pathway cancer is more common, it produces about 80% of all microsatellite-unstable tumors. Current recommendations are to screen all colorectal cancers for MSI or failed expression of mismatch repair proteins. Positive tests for MSI or failure to express mismatch repair protein MLH1 should be followed by BRAF mutation tests or hypermethylation assays to distinguish MSI arising through the Lynch pathway from MSI arising through the serrated pathway.

In the current study, researchers tested 253 surgically resected colorectal cancer specimens for failed expression of mismatch repair proteins, and in some cases for microsatellite instability, and examined the results by race and Hispanic ethnicity group.

The prevalence of mismatch repair deficiency was similar across groups: 9.6% among 73 black non-Hispanic patients, 10.4% among 77 non-Hispanic white patients, and 12.6% among 103 Hispanic patients. MSH2 deficiency was more common in Hispanic patients compared with non-Hispanic patients.

Citation(s):

Sussman DA et al. Colorectal tumors from different racial and ethnic minorities have similar rates of mismatch repair deficiency. Clin Gastroenterol Hepatol 2016 Apr 1; [e-pub].

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