Comparison of sentinel lymph node distribution and lymphatic drainage pathway between high- and low-risk endometrial cancers.

PURPOSE: This study aimed to compare the distribution and drainage pathway of sentinel lymph nodes between high- and low-risk endometrial cancers. METHODS: In total, 429 patients with endometrial cancer who underwent sentinel lymph node biopsy in Peking University People's Hospital from July 2015 to April 2022 were retrospectively enrolled. There were 148 patients in the high-risk group and 281 patients in the low-risk group. RESULTS: The unilateral and bilateral detection rates of sentinel lymph nodes were 86.5% and 55.9%, respectively. The highest detection rate was achieved in the subgroup with a combined use of indocyanine green (ICG) and carbon nanoparticles (CNP) (94.4% for unilateral detection and 66.7% for bilateral detection). The upper paracervical pathway (UPP) was detected in 93.3% of cases in the high-risk group and 96.0% of cases in the low-risk group (p = 0.261). The lower paracervical pathway (LPP) was detected in 10.0% of cases in the high-risk group and 17.9% of cases in the low-risk group (p = 0.048). Remarkably increased detection rates of SLN in the common iliac (7.5%) and para-aortic or precaval areas (2.9%) were observed in the high-risk group. In contrast, a markedly decreased detection rate of SLN in the internal iliac area (1.9%) was observed in the high-risk group. CONCLUSION: The highest detection rate of SLN was observed in the subgroup with a combined use of ICG and CNP. The detection of UPP is important for both high-risk and low-risk cases, while LPP detection plays a more important role in the low-risk group. Lymphadenectomy in the common iliac and para-aortic or precaval areas is essential for patients with high-risk EC. Removal of internal iliac lymph nodes is essential for patients with low-risk EC, in case of ineffective SLN mapping.