DNA Mismatch Repair Deficiency in Colorectal Adenocarcinoma: an Evaluation Test for Suspecting Lynch Syndrome

Aim: To profile the clinical and pathological characteristics, as well as to determine the prevalence of failed repair of deoxyribonucleic acid incompatibility by immunohistochemistry, of people diagnosed with colon adenocarcinoma at an age of < 70 years and to assess the detection of suspected cases of Lynch syndrome using immunohistochemistry by comparing all cases with those that only meet criteria clinical and pathological of suspicion.

Methods: An observational and cross-sectional study was carried out that included 249 patients, whose demographic characteristics, personal and family history of cancer, compliance with the Amsterdam, Bethesda and PREMM5 criteria, as well as the pathological characteristics of colorectal adenocarcinoma were analyzed. The prevalence of the immunohistochemical alteration of the MLH1, MSH2, MSH6 and PMS2 proteins that was compatible with a suspected case of Lynch syndrome was determined, and the probability and agreement of finding this alteration according to the clinical-pathological variables was estimated.

Results: The use of immunohistochemistry showed a prevalence of 22 cases (8.8%) with a suspected alteration of Lynch syndrome. Of these cases, none met all the clinical-pathological criteria for suspicion of the syndrome. Alternatively, most of the participants who met the criteria for suspicion did not have an alteration in the tests. It was shown that there is a higher prevalence of the alteration in immunohistochemistry when the cancer is located right (proximal to the splenic angle) and when Bethesda criteria 3 or 4 are met. It was documented that there is a null to low agreement between the clinical criteria and immunohistochemistry.

Conclusion: These findings suggest that immunohistochemistry testing in patients with colorectal adenocarcinoma could identify more candidates for complementary studies to confirm Lynch syndrome, regardless of the clinical and pathological criteria that are usually used to select who undergoes this immunohistochemistry test.