Introduction This retrospective study aimed to confirm the clinical impact of ultrastaging of sentinel lymph node (SLN) mapping with Indocyanine green (ICG) injection in patients with endometrial cancer (EC).

Methods This retrospective study obtained data from the electronic medical records of Severance Hospital. The subjects included patients with EC who have undergone surgical staging with SLN mapping using ICG injection between June 2014 to December 2017 at Severance Hospital. The SLN paraffin blocks were sliced into two or three layers at an interval of 200 μm between the layers by 3 μm thickness. The immunohistochemistry was performed with anti-cytokeratin antibodies AE1/AE3.

Results A total of 138 patients included (no metastasis (NM), n=124, 89.9%; macro-metastasis (MAC), n=2, 1.4%; micro-metastasis (MM), n=11, 8.0%; isolated tumor cells (ITC), n=1, 0.7%). A total of 1006 paraffin blocks were examined (NM, n=984, 97.8%; MAC, n=2, 0.2%; MM, n=13, 1.3%; ITC, n=7, 0.7%). The 5-year disease-free survival significantly differed according to the results of ultrastaging (NM, 94.9%; MAC and MM, 69.2%; p<0.001). The 5-year overall survival was no significant difference in the status of ultrastaging (NM, 97.4%; MAC and MM, 100%; p=0.579). Analyzing the Cox proportional hazards model, the prognostic factor of recurrence was ultrastaging (Hazard Ratio 5.70, [95% Confidence Interval 1.50–21.68], p=0.011). The ultrastaging had no prognostic impact on the overall survival.

Conclusion/Implications The ultrastaging detected more MAC, MM, and ITC of SLN and was a prognostic factor of recurrence in patients with EC. Further study is needed for the clinical impact of ultrastaging for adjuvant therapy of EC.