“…Approximately 20 200 women in the United States who undergo hysterectomy receive a primary hospital discharge diagnosis of EH each year (Keshavarz et al, 2002), but progression risks for EH have not been accurately characterised in rigorous populationbased studies (Silverberg, 2000). Current management of EH relies on largely historical data from studies that lacked adequate control groups (Kurman et al, 1985;Feldman et al, 1995;Terakawa et al, 1997;Tabata et al, 2001;Horn et al, 2004;Baak et al, 2005) and were limited by sample size (Feldman et al, 1995;Tabata et al, 2001), short follow-up (Feldman et al, 1995;Terakawa et al, 1997;Tabata et al, 2001), suboptimal statistical methods (Kurman et al, 1985;Pettersson et al, 1985;Feldman et al, 1995;Terakawa et al, 1997;Tabata et al, 2001;Horn et al, 2004), and minimal clinical and treatment information (Kurman et al, 1985;Pettersson et al, 1985;Terakawa et al, 1997;Tabata et al, 2001;Horn et al, 2004). Endometrial hyperplasia diagnoses can misclassify disease severity because of biopsy sampling errors (Zaino, 2000;Trimble et al, 2006;Zaino et al, 2006) or the community pathologists' reported tendency to overestimate lesion severity (Silverberg, 2000).…”