Predictors of non-sentinel lymph node (non-SLN) metastasis in patients with sentinel lymph node (SLN) metastasis in endometrial cancer

•SLN mapping may be superior to traditional lymphadenectomy as a staging procedure.•SLN mapping has a high detection rate, sensitivity and negative predictive value.•Size of the SLN metastasis is the strongest predictive factor of non-SLN involvement.

ObjectivesThe aim of this study was to determine the risk of metastasis in the remaining non-SLNs when the SLN is positive and to identify the factors that can predict this risk.MethodsWe reviewed all patients who underwent primary surgery for endometrial carcinoma with lymphadenectomy and SLN mapping (November 2010-November 2013) in our center. SLNs were ultra-staged on final pathology.ResultsA total of 268 patients were included. Overall, 43/268 patients (16%) were found to have SLN metastasis: macro-metastasis in 24 patients, micro-metastasis in 7 and ITC in 12. Non-SLN metastases were found in 15 of the 43 patients (34.8%) with positive SLN. Size of the SLN metastasis was the only factor associated with an increased likelihood of non-SLN metastasis (p = 0.005). When the size of the SLN metastasis was ≤ 2 mm, the risk of having another positive lymph node was only 5%, conversely, when the size of the SLN metastasis was > 2 mm, the risk of having another positive lymph node was 60.8% (p < 0.0001). Histologic type, grade, depth of myometrial invasion, LVSI, cervical stromal invasion and CA-125 were not predictive.ConclusionWhen the SLN is positive, the risk of metastasis in the remaining non-SLNs was 34.8%. Size of the metastasis within the SLN was the only factor that could predict the risk of non-SLN metastasis; 2 mm seems to be the cutoff size below which the risk of non-SLN metastasis is low.