Variability in Sentinel Lymph Node Locations in Endometrial Cancer: A Single-Center Study and Literature Review

Background Sentinel lymph node biopsy (SLNB) has become a widely accepted alternative to systematic lymphadenectomy in endometrial cancer (EC), reducing surgical morbidity without compromising diagnostic accuracy. However, the anatomical variability of sentinel lymph node (SLN) locations remains insufficiently understood, with substantial differences reported across studies. This study analyzed SLN distribution in a large single-center cohort and compared the findings with published data. Methods We retrospectively analyzed 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 (Tc99m), 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 (17.1%) nodes. The use of tracer combinations (ICG + Tc99m or Tc99m + Patent Blue) improved detection when preoperative Tc99m mapping was incomplete. Para-aortic SLNs were rare (1.5%) but carried a significantly higher risk of metastasis. Conclusions SLNB 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 optimize SLNB in gynecologic oncology.