A study on uterine lymphatic anatomy for standardization of pelvic sentinel lymph node detection in endometrial cancer

Objective: To describe the anatomy of uterine lymphatic drainage following cervical or fundal tracer injection to enable standardization of a pelvic sentinel lymph node (SLN) concept in endometrial cancer (EC). Methods: A prospective consecutive study of women with EC was conducted. A fluorescent dye (Indocyanine green) was injected into the cervix (n = 60) or the uterine fundus (n = 30). A systematic trans- and retroperitoneal mapping of uterine lymphatic drainage was performed. Positions of the pelvic SLNs, defined by afferent lymph vessels, and lymph node metastases were compared. Results: Two consistent lymphatic pathways with pelvic SLNs were identified irrespective of injection site; an upper paracervical pathway (UPP) with draining medial external and/or obturator lymph nodes and a lower paracervical pathway (LPP) with draining internal iliac and/or presacral lymph nodes. Bilateral display of at least one pelvic pathway following cervical and fundal injection occurred in 98% and 80% respectively (p = 0.005). Bilateral display of both pelvic pathways occurred in 30% and 20% respectively (p = 0.6) as the LPP was less often displayed. Nearly one third of the 19% node positive patients had metastases along the LPP. No false negative SLNs were identified. Conclusions: Based on uterine lymphatic anatomy a bilateral detection of at least one SLN in both the UPP and LPP should be aimed for. Absence of display of the LPP may warrant a full presacral lymphadenectomy. Although pelvic pathways and positions of SLNs are independent of the tracer injection site, cervical injection is preferable due to a higher technical success rate.