Endometrial cancer with positive sentinel lymph nodes: pathologic characteristics of metastases as predictors of extent of lymphatic dissemination and prognosis

To assess predictors of extensive lymph node dissemination and non-vaginal recurrence in patients with endometrial cancer with positive sentinel lymph nodes (SLNs). Patients with endometrial cancer who underwent primary surgery with SLN mapping and had at least one positive node between October 2013 and May 2019 were included. Positive SLNs were reviewed, and cases were classified according to the location of the metastasis (extracapsular vs intracapsular), and the size of the largest SLN metastasis (isolated tumor cells, micrometastasis, macrometastasis). Associations were assessed based on fitting logistic regression models and Cox proportional hazards models. A total of 103 patients met the inclusion criteria: including 36 (34.9%) with isolated tumor cells, 27 (26.2%) with micrometastasis, and 40 (38.8%) with macrometastasis. Notably, 71.4% of patients exhibiting extracapsular SLN metastases had multiple positive SLNs (p=0.008). Extracapsular invasion (adjusted odds ratio (aOR) 5.81, 95% CI 1.4 to 23.6) and age (aOR=1.8, 95% CI 1.1 to 3.0) emerged as independent predictors of multiple positive SLNs. Among the 38 patients who underwent a backup pelvic lymphadenectomy, 18 (47.4%) presented with positive pelvic non-SLNs, a phenomenon more prevalent in patients with macrometastasis (p=0.004). Independent predictors of non-vaginal recurrence included SLN macrometastasis (adjusted hazard ratio (aHR) 3.3, 95% CI 1.3 to 8.3), non-endometrioid histology (aHR=3.7, 95% CI 1.5 to 9.3), and cervical stromal invasion (aHR=5.5, 95% CI 2.0 to 14.9). Among the 34 patients with isolated tumor cells and endometrioid histology, 3 (9%) experienced a recurrence, all of whom had not received any adjuvant chemotherapy or external beam radiotherapy. Patients with positive SLN macrometastasis are independently associated with extensive lymphatic dissemination and distant recurrences. The risk of multiple positive SLNs increases with the extracapsular location of the SLN metastasis and with age. Independent uterine pathologic predictors of non-vaginal recurrence are non-endometrioid histology and cervical stromal invasion.