Progression of endometrial hyperplasia: A revisit under the 2014 WHO classifications

273 patients diagnosed with endometrial hyperplasia from 1999-2001 at our institution were classified using the 1994 and 2014 WHO criteria. By 1994 criteria: 189 patients had simple hyperplasia (SH), 8 had simple hyperplasia with atypia (SHA), 23 had complex hyperplasia (CH), and 53 had complex hyperplasia with atypia (CHA). By 2014 criteria: 212 patients had benign endometrial hyperplasia (BEH) and 61 patients had atypical endometrial hyperplasia/endometrioid intraepithelial neoplasia (AEH/EIN). The primary endpoint was development of endometrioid carcinoma. With a median follow-up of 5.2 years, progression to endometrioid carcinoma occurred in 1.6% of patients with SH, 25% with SHA, 4.3% with CH, 24.5% with CHA, 1.9% with BEH and 24.5% with AEH. In patients that did not undergo hysterectomy for at least 1-year, 20% with AEH and 2.6% with BEH progressed to carcinoma. Patients with CHA had a shorter endometrioid carcinoma free survival time (EFS) than patients with SH (P < 0.0001) but was not different from SHA (P = 0.78) or CH (P = 0.02) after correction for multiple comparisons. Patients with SHA had a shorter EFS than patients with SH (P < 0.0001) but was not different from CH (P = 0.12). Patients with SH did not have a shorter EFS than patients with CH (P = 0.30). Median EFS was shorter in patients with AEH (10.9 years) than patients with BEH (16.3 years, HR = 0.08, 95% CI: 0.008 to 0.08, P < 0.0001). While confirming the diagnostic validity of both schemes, our data support the emphasis on cytological atypia by the two-tiered 2014 WHO classification.