Does the Two-Tier System Accurately Predict Progression of Endometrial Hyperplasia to Endometrial Carcinoma in High-Risk Populations? A Retrospective Study in a Safety-Net Hospital

Introduction/Objective In 2014, the WHO simplified the classification of endometrial hyperplasia (EH) into a two-tier system: endometrial hyperplasia without atypia/benign endometrial hyperplasia (BEH) and atypical endometrial hyperplasia (AEH)/endometrioid intraepithelial neoplasia (EIN), as opposed to the 1994 WHO 4-tier scheme. We conducted this study to assess the diagnostic validity of the two-tier scheme in predicting upgrade to endometrioid adenocarcinoma (EA) in our high-risk patient population. Methods Retrospective review from Aug 2009 to August 2019 revealed 144 cases of EH diagnosed on biopsy. The cases were reclassified using the 2014 two-tier scheme to 81 BEH and 63 AEH. The excisional diagnoses, if available, were compared with the initial biopsy results. Results At hysterectomy, 22 AEH (50%) were diagnosed as benign, with no residual AEH, 15 cases were upgraded to EA (34.1%), and 7 had residual AEH (15.9%). Endometrial polyp was identified in 29 cases out of 63 AEH, 24 of which had a follow-up excision. Among those, 6 were upgrade to EA (25%), significantly lower than the upgrade rate of AEH without polyp (45%) (p=0.0344). Conclusion In our high-risk patient population, the likelihood of upgrade to EA at excision of a biopsy-diagnosed AEH is significantly higher than BEH and is in line with what was reported in the literature for other populations. Patients with endometrial polyps were less likely to progress to EA. Our study demonstrated the diagnostic validity of the two- tiered classification in high-risk population and supports the emphasis on cytological atypia.