A case report and literature review of duodenal adenocarcinoma with complete loss of mismatch repair proteins

We represent a molecularly validated case of dMMR duodenal adenocarcinoma, suggesting a somatic molecular pathogenesis distinct from classic intestinal cancer. The findings highlight the critical importance of comprehensive molecular characterization in rare tumors, as accurate identification of these phenotypes are important for optimal treatment selection, particularly immune checkpoint inhibitor therapies for gastrointestinal malignancies.