Sentinel lymph node distribution in endometrial cancer: clinical patterns and implications from a 292-patient cohort.

BACKGROUND: Sentinel lymph node biopsy (SLNB) is an established alternative to systematic lymphadenectomy in endometrial cancer (EC). However, the anatomical variability of sentinel lymph node (SLN) locations remains incompletely characterised. This study assessed SLN distribution in a single-centre cohort and compared findings with published data. MATERIALS AND METHODS: We retrospectively analysed 292 patients with EC treated at the Maria Sklodowska-Curie National Research Institute of Oncology, Krakow Branch (2016-2025). All underwent SLN mapping using technetium-99m (Tc-99m), indocyanine green (ICG), Patent Blue, or their combinations. Bilateral detection failures were managed according to an established intraoperative algorithm. SLNs were classified anatomically, and outcomes were compared across mapping techniques. Histopathological assessment included ultrastaging. RESULTS: A total of 526 SLNs were identified (mean 1.8 per patient). The most common locations were the obturator (48.7%) and internal iliac (25.1%) regions. Bilateral detection was achieved in 87.0% of patients, unilateral in 12.0%, and no detection in 1.0%. Metastases were found in 41 SLNs (7.8%) from 34 patients (11.6%), most frequently in obturator (41.5%) and internal iliac (14.6%) nodes. The use of tracer combinations (ICG + Tc-99m or Tc-99m + Patent Blue) improved detection when preoperative Tc-99m mapping was incomplete. Para-aortic SLNs were rare (1.5%) but carried a significantly higher risk of metastasis. CONCLUSIONS: Sentinel lymph node biopsy is an effective and safe method for nodal assessment in EC, with the obturator and internal iliac regions being the most frequent SLN sites. Variability in SLN locations appears to depend on mapping technique, tracer type, and surgical access. Standardization of procedures and prospective comparative studies are essential to further optimise SLNB in gynaecological oncology.