Pathological diagnosis experience and literature review of four cases suspected Lynch-like syndrome

Extraintestinal tumors associated with Lynch-like syndrome mostly exhibit histopathological characteristics and MMR/MSI changes similar to classic Lynch syndrome, but without pathogenic germline MMR mutations or <i>MLH1</i> promoter methylation. Some suspected Lynch-like syndromes with likely germline pathogenic MMR mutations may represent Lynch syndrome with atypical phenotype. Most cases lack germline MMR mutations in normal tissues but harbor somatic MMR mutations in tumor tissues. Germline or somatic mutations in other genes related to MMR function may be observed in some cases.