[<p>Lynch syndrome is a major cause of monogenetic familial colorectal cancer</p>].

Individuals with a history of colorectal or endometrial cancer younger than 50 years of age or with relatives younger than 50 years of age with a history of any of these malignances should be referred to clinical genetics for further diagnostic examinations and genetic counseling. Lynch syndrome is caused by mutations in mismatch repair genes and implicates an increased risk for colorectal cancer as well as endometrial cancer. Routine surveillance for this group of individuals regarding colorectal cancer by means of colonoscopy and endometrial cancer by means of transvaginal ultrasound as well as endometrial biopsies is recommended annually or biennially. Several preventive measures are under development, such as chemoprevention and vaccination. During 2015 we investigated reasons for diagnosis among those registered at Karolinska University Hospital. We found that a substantial part of this group of individuals was diagnosed in conjunction with their diagnosis of cancer; a prerequisite in order to offer at-risk individuals preventive measures is to improve identification of these individuals and offer them presymptomatic genetic testing in order to identify predisposing mutations.