Endometrial Intraepithelial Neoplasia

Context.-Developed in conjunction with molecular and progression data, the sequence classification schema for endometrial intraepithelial neoplasia (EIN)/benign hyperplasia (BH) provides an easy to adopt and reproducible method for classification of endometrial biopsies. Objectives.-To review current data supporting the use of BH/EIN to classify endometrial biopsies, and to discuss the hormone-driven endometrial sequence from anovulation/disordered proliferative endometrium through BH and EIN and their diagnostic difficulty. Data Sources.-A comprehensive review of EIN literature based on literature indexed by PubMed (National Library of Medicine) and Google Scholar. Conclusions.-The BH/EIN schema is gaining wider acceptance among pathologist and clinicians. The research leading to the EIN criteria is based on molecular and progression data. The BH/EIN schema has better reproducibility among pathologists, is intuitively easy to use, and requires understanding of endometrial physiology and neoplasia.