The histological diagnosis of endometrial hyperplasia. Is there a need to simplify?

The intra- and interobserver variability of the histological diagnosis of endometrial hyperplasia, including low-grade carcinomas, is high and thus often causes confusion in the dialogue between pathologists and clinicians. The current classification of the WHO, ISGP, and FIGO is not altogether successful in overcoming this difficulty. New approaches to resolve this unsatisfactory situation have been suggested by two recent simultaneous studies, one by a European group of experts (1999) and the other by Mutter and The Endometrial Collaborative Group (2000). Both studies suggest simplifying the WHO classification by reducing the present four categories to two. The European study names the new histological groups endometrial hyperplasia (EH) and endometrioid neoplasia (EN), while Mutter et al. call them endometrial hyperplasia (EH) and endometrial intraepithelial neoplasia (EIN). Differentiation between the two new categories can be made based on uncomplicated morphological concepts and confirmed morphometrically by the semiquantitative determination of the stromal volume in relation to total tissue volume (stroma+epithelium+gland lumen). This simplification has the advantage of a high degree of reproducibility of histological diagnoses while facilitating understanding by clinicians. Most importantly, there is no decrease in prognostic accuracy, since EH is a benign lesion, easily treated with hormones and almost without risk of progressing to cancer, while EIN/EN is a pre- or already malignant disease with a high risk of progression (approximately 30%) requiring a more radical treatment. This article summarizes the current discussion on this issue.