Introduction Endometrial cancer is the most common gynecologic malignancy worldwide, and lymph node metastasis is a major prognostic factor for patients with this cancer. Mismatch repair (MMR) deficiency is known to play a critical role in the development of endometrial cancer, but its association with lymph node metastasis and recurrence remains unclear. In this study, we aimed to investigate the correlation between MMR status and lymph node metastasis/recurrence rate in endometrial cancer.

Methods We retrospectively analyzed 59 patients with endometrial cancer who underwent surgery and received MMR testing at out institution between 2010 and 2022. Immunohistochemistry was performed to assess the expression of MMR, including MLH1, PMS2, MSH2, and MSH6.

Results Of these patients, 14 (23.7%) had MMR deficiency. The MMR deficient group had a higher proportion of early stage (stage I and II) compared to the MMR proficient group (78.6% vs. 64.4%). However, lymph node metastasis was more common in the MMR deficient group (21.4%) compared to the MMR proficient group (13.3%) (p=0.038). Furthermore, the recurrence rate was higher in the MMR deficient group (21.4% vs. 15.6%).

Conclusion/Implications Therefore, MMR status may serve as a useful biomarker to predict the risk of lymph node metastasis and recurrence in patients with endometrial cancer. Based on our findings, knowing the MMR status before surgery may help in determining an appropriate surgical plan, which could potentially improve the prognosis and quality of life of the patients. Further studies with larger sample sizes are needed to validate our findings.