This study analyzed the differences in clinical baseline features and survival outcomes between pMMR and dMMR patients. The aim is to evaluate the impact of MMR status on overall survival and disease-free survival of colorectal patients, and to explore the population exempt from extended resection, so as to provide evidence-based medical evidence for the relationship between MMR status, lymph node metastasis pattern and clinicopathological risk factors in colon cancer patients.

In recent years, colorectal cancer has become one of the most common cancers worldwide, and its prevalence and mortality are among the top three malignant tumors . Mismatch repair protein is considered to be one of the risk factors affecting the development of colorectal cancer, including MSH2, MSH6, MLH1, PMS2 and so on. However, their exact relationship to lymph node metastasis in patients with colorectal cancer is unclear. Studies have found that loss of expression of mismatch repair protein and positive expression of Her-2 are associated with lymph node metastasis in patients with colorectal cancer. On the other hand, MSI-H/dMMR colorectal cancer patients have a similar set of pathological features , such as the right half colon is more common, and lymph node or distant organ metastasis is less, but the relationship between the loss of mismatch repair status and skipping lymph node metastasis and other factors such as cancer nodules, nerve tract infiltration, and vascular cancer embolus has been ignored.

Right hemicolectomy combined with regional lymph node dissection is the standard operation for right hemicolectomy.However, there is no consensus on the scope of dissection, and different guidelines put forward different recommendations. For example, complete mesocolic excision (CME) combined with central vessel ligation (CVL) is recommended in Europe and the United States, while D3 surgery proposed by Japan has a large surgical risk. The surgical practice in China is consistent in principle with CME, but the scope of lymph node dissection tends to follow the Japanese D2/D3 scope of dissection, resulting in the lack of uniform standard.

Some studies have shown that expanding the scope of lymph node dissection can reduce the risk of local recurrence and distant metastasis, but this advantage is more significant in stage I to II patients, and there is no statistical difference in stage III colon cancer. At the same time, some studies have questioned the necessity of D3 dissection, arguing that the central group of lymph node metastasis is not significant, so D3 dissection is an overtreatment.

Therefore, the relationship between MMR status, lymph node metastasis pattern and clinicopathological risk factors in colon cancer patients needs to be further studied. Such research helps to stratify the management of patients at different risks and develop the most effective lymphatic dissection program for them, so as to provide individual and most appropriate treatment for each patient, in order to achieve the best treatment outcome and prognosis.

Inclusion Criteria:

• The preoperative diagnosis was primary colon adenocarcinoma;
• Undergoing radical surgical treatment;
• Postoperative immunohistochemistry to determine MMR status;
• Having complete key clinical and follow-up data.

Exclusion Criteria:

• Previous history of malignant tumors
• Concurrent distant metastasis
• Receiving preoperative neoadjuvant therapy.

The study subjects were colon cancer patients who received radical surgical treatment at the Sixth Affiliated Hospital of Sun Yat-Sen University from January 2010 to December 2021. Patients must not have received neoadjuvant chemoradiotherapy and have a clear MMR status and necessary clinical and pathological information as well as follow-up prognostic information

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