A selective anatomically based lymph node sampling can replace a side specific pelvic lymphadenectomy in endometrial cancer with failed sentinel node mapping.

Aim To evaluate the locations of metastatic pelvic sentinel nodes (SLN) and the proportion of SLNs outside and within defined typical anatomical positions along the upper paracervical lymphatic pathway (UPP). Patients and Methods Consecutive women with endometrial cancer (EC) of all risk groups underwent pelvic SLN-detection using cervically injected indocyanine green (ICG). A strict anatomically based algorithm and definitions of SLNs was adhered to. The positions of ICG-defined SLNs were intraoperatively depicted on an anatomical chart. All SLNs were examined using ultrastaging and immunohistochemistry. The proximal third of the obturator fossa and the interiliac area were defined as typical positions. The parauterine lymphovascular tissue (PULT) was separately removed. The proportions of metastatic SLNs, overall and isolated, typically, and atypically positioned were analyzed per woman. Results A median of two (range 1-12) SLN metastases along the UPP including the PULT were found in 162 women. 41 of 162 women (25.3%) had isolated metastases in the obturator fossa harboring 49.1 % of all SLN metastases. Three women (1,9%) had isolated PULT metastases. SLN metastases outside typical positions were identified in 28/162 women (17.3%); isolated metastases were seen in seven women (4.3%), so 95.7% of pelvic node positive women had at least one metastatic SLN located at a typical position. Conclusion A selective removal of lymph nodes at typical proximal obturator and interiliac positions and the PULT can replace a full side specific pelvic LND when SLN mapping is unsuccessful. The obturator fossa is the predominant location for metastatic disease.