DNA Mismatch Repair and Lynch Syndrome

Purpose of Review: This review will discuss the genetic basis and epidemiology of Lynch syndrome, review Lynch Syndrome colorectal cancer screening guidelines, and summarize the screening guidelines pertaining to other cancers that are associated with Lynch syndrome. Recent Findings: All colorectal tumors should be universally tested for microsatellite instability (MSI) changes regardless of the age of the patient. Genetic testing of family members of patients with Lynch syndrome has significant cost effectiveness implications. Polyethylene glycol bowel preparation and chromocolonoscopy improve screening exams. Aspirin use is associated with decreased colorectal cancer risk. Phosphodiesterase-1 (PD-1) inhibitor immunotherapy is effective treatment in mismatch repair (MMR) deficiency tumors. Summary: Lynch syndrome should be suspected if patients with malignancies exhibit diagnostic criteria and these tumors should be tested for MMR deficiencies. Colonoscopy is used for surveillance of colorectal cancers in Lynch syndrome, and bowel preparation quality and colonoscopy techniques are important factors contributing to efficacy. Clinicians should be aware of screening modalities for extracolonic cancers including upper endoscopy, regular transvaginal ultrasound with endometrial sampling, and urinalysis.