Size of Sentinel Node Metastasis Predicts Non-sentinel Node Involvement in Endometrial Cancer.

Purpose: To analyze the relationship between the size of metastatic sentinel lymph nodes (SLNs) and the risk of non-sentinel lymph node (non-SLN) metastasis in endometrial cancer.
Patients and Methods: From a total of 328 patients with endometrial cancer who underwent SLN mapping from January 2013 to April 2019, 142 patients also underwent systematic completion pelvic ± paraaortic node dissections, and they form the basis of this study. The SLNs were examined by immunohistochemistry (IHC) when the hematoxylin-eosin stain was negative.
Results: The median age was 60 years. The overall detection rate for SLNs was 87.5%, and bilateral SLNs were observed in 66.2%, with a median of 2 SLNs resected (range 1-8). Twenty-nine (20.4%) cases had positive SLNs, with a median of one positive SLN. Regarding the size of SLN metastasis, 5 (3.5%) cases had isolated tumor cells (ITCs), 13 (9.2%) had micrometastases, and 11 (7.7%) had macrometastases. Notably, 14/29 (48.3%) had node metastases that were detected after IHC. Eight (27.6%) patients had positive non-SLNs, with a median count of 7 positive nodes (range 2-23). Regarding the size of SLN metastasis, non-SLN involvement was not present in cases with ITC (0/5) but was present in 15.4% (2/13) of cases with micrometastases and 54.5% (6/11) of cases with macrometastases. The only risk factor for positive non-SLNs was the size of SLN metastasis.
Conclusions: Our data suggest that size of SLN metastasis is associated with the risk of non-SLN metastasis. No patients with ITCs in SLNs had another metastatic lymph node in this study.