Management of Endometrial Intraepithelial Neoplasia: A Retrospective Review of Practice Patterns at a Single Military Treatment Facility and Civilian Partner Hospital.

Background: Endometrial intraepithelial neoplasia (EIN) is a known precursor to endometrial endometrioid carcinoma, with a 40% risk of concurrent endometrial cancer at the time of hysterectomy. Many benign gynecologists (GYN) refer to gynecologic oncologists (GYO) for this risk of malignancy. This retrospective cohort study describes the pathological outcomes of patients with EIN who underwent hysterectomy at a single military treatment facility (MTF) and a civilian partner hospital. Methods: A retrospective chart review was performed for patients with a diagnosis of EIN at a single MTF and civilian hospital from 1/1/2021 to 10/30/2023. Preoperative risk factors for malignancy of cases performed by GYN and GYO were compared. Results: A total of 58 patients with EIN were included (8 from the MTF, 50 from the civilian partner hospital). Of these, 48 (82.8%) patients were referred to GYO for hysterectomy. Thirty-three (56.9%) patients were upstaged to endometrial cancer, with 28 (84.5%) Stage IA, 3 (9.1%) Stage IB, and 2 (3.4%) Stage III. Of the 48 patients in the GYO cohort, 36 patients underwent nodal sampling with only one lymph node positive for metastasis. No patients required secondary staging procedures. No significant preoperative risk factors were identified for advanced cancer. Conclusions: Our data supports prior literature suggesting that the likelihood of nodal involvement and advanced metastatic disease in patients with EIN is low. Current guidelines allow flexibility in the management of EIN by either GYN or GYO. Additional research into and application of preoperative risk algorithms may help identify patient risk for advanced malignancy and accurately guide low-risk patients towards management by GYN and high-risk patients by GYO.