Prevalence of MLH1 constitutional epimutations as a cause of Lynch syndrome in unselected versus selected consecutive series of patients with colorectal cancer

Lynch syndrome is a hereditary condition which predispose to colorectal cancer and other tumors. A particular cause of this syndrome is the MLH1 constitutional methylation (epimutation). Universal tumor testing is recommended as the best strategy to identify Lynch syndrome patients. This screening renders a considerable number of cases with MLH1 methylation in tumors raising the question to test or not, for constitutional epimutation. Our results suggest that the prevalence of constitutional epimutation is negligible in colorectal cancer patients who do not fulfil the risk criteria, rendering this testing unnecessary in members of the general population who lack cancer history or are aged at the time of diagnosis. (By Dr. José Luis Soto, http://jmg.bmj.com/content/early/2015/04/23/jmedgenet-2015-103076 )