Lynch综合征是一种常染色体显性遗传性疾病，因DNA错配修复基因（mismatch repair，MMR）存在胚系突变导致大肠癌、子宫内膜癌等相关肿瘤的遗传易感，虽然该病总体所占比例不高（仅3%~5%大肠癌/内膜癌属Lynch综合征），但对这部分病例的正确诊断将使患者及家人受益。本文结合文献及国际诊疗指南报道了两例Lynch综合征，这两例患者的大肠癌和内膜癌具有不同的临床病理特点及MMR蛋白失表达，结合文献提示，Lynch综合征的子宫内膜癌和大肠癌，两者MMR基因突变、蛋白失表达、相关分子机制特点及生物学行为不完全一致，故临床筛查策略与流程也不尽相同，免疫组织化学筛查方法简单易行，在大肠癌和内膜癌这些临床常见的肿瘤中进行筛查，可发现肿瘤易感人群，临床意义重大。

SUMMARYLynch syndrome is an autosomal dominant genetic disease characterized by the early onset of colon cancer, endometrial cancer and other tumors caused by a genetic mutation within DNA mismatch repair (MMR) genes. A small subgroup (approximately 3%-5%) of endometrial cancer and colorectal cancer is related to Lynch syndrome. Identification of these patients in clinical practice will be of great benefit to the relatives and patients themselves. We reported two cases, and reviewed the literature and clinical diagnostic guideline. MMR protein was lost in the tumors. Meanwhile the two cases had different clinicopathological characteristics. Together with the literature, our findings may suggest that the MMR protein expression, associated molecular alterations and clinicopathological features and biological behavior of endometrial cancer and colorectal cancer related to Lynch syndrome are different. Thus the algorithm for detection the patients at highest risk is different. To detect the MMR loss by immunohistochemistry is a practicalscreening method.