Defining “enlarged” sentinel lymph nodes in the setting of endometrial cancer: What is the size cut-off?

Background: Sentinel lymph node (SLN) mapping has become standard-of-care in endometrial cancer surgical staging. While removal of “enlarged” lymph nodes is recommended regardless of SLN mapping, there is no data to support definitive size criteria for intra-operative assessment. We sought to assess the size of negative and positive SLN in surgically-staged endometrial cancer patients. Methods: Surgically-staged endometrial cancer patients undergoing SLN assessment of at least one hemipelvis at a single comprehensive cancer center were retrospectively reviewed from 2017 to 2020. SLN were categorized as negative (benign) or positive (metastatic). SLN size was defined as the largest diameter (cm) of the SLN as measured in the gross description of the surgical pathology report. Size of negative and positive SLN was compared using descriptive statistics. Results: Of 597 patients, 575 had an evaluable negative SLN, and median size was 2.0 cm [0.4–4.5 cm]. 39 patients had an evaluable positive SLN, and median size was 2.1 cm [0.5–4.9 cm]. Lymph node size ≥2 cm was 67 % sensitive and 49 % specific for detecting metastatic disease. Age < 50 and BMI ≥30 were associated with larger lymph node size (p = 0.04 and p = 0.028, respectively). For evaluable positive SLN, mismatch repair (MMR) IHC (n = 39), and p53 IHC (n = 18) did not impact size (p = 0.71 and p = 0.83, respectively). Conclusions: Negative and positive SLN are similar in size, thus SLN size is a poor predictor of metastasis in patients undergoing surgical staging of endometrial cancer. Intra-operative assessment of size should not serve as sole indication for targeted lymph node removal.