Constitutional MLH1 Methylation Is a Major Contributor to Mismatch Repair–Deficient, MLH1-Methylated Colorectal Cancer in Patients Aged 55 Years and Younger

Abstract

Although rare overall, a significant proportion of younger patients with MLH1-methylated CRC had underlying constitutional MLH1 methylation. Routine testing for this high-risk mechanism is warranted in patients aged ≤55 years for a timely and accurate molecular diagnosis that will significantly alter their clinical management while minimizing additional testing.