**1. Introduction**

Endometrial hyperplasia (EH) is defined as an irregular proliferation of the endometrial glands leading to an increase in the gland-to-stroma ratio in contrast to proliferative endometrium.

The histological classification of EH has undergone numerous changes over the years, reflecting its diagnostic complexity and making it difficult to compare studies performed with different classifications. In 2014, the World Health Organization (WHO) suggested a dichotomous classification of EH [1], which was accepted by the International Society of Gynecological Pathologists, to reduce the multitude of terms used worldwide. EH has been

divided into two groups: non-atypical EH/benign hyperplasia and atypical EH (AEH) or Endometrial Intraepithelial Neoplasia (EIN) according to the presence or absence of atypical cytological features. AEH is a premalignant lesion, with an approximately 30% risk of progression to endometrial carcinoma (EC) [2,3]. The prevalence of concurrent occult EC in patients diagnosed with AEH undergoing hysterectomy approaches 43% [4]. EC is the most common gynecologic cancer in women; it is a more common disease among postmenopausal women, but in the last few years, there has been a rise in the number of EC among premenopausal women [5]. EC is more prevalent in high/intermediate-developed countries [6].

Preoperative diagnostics play a central role in defining the correct treatment course of action and surgical approach of AEH and EC. For instance, although lymph node evaluation remains crucial in the surgical management of endometrial carcinoma, there remain no clear consensus guidelines regarding nodal evaluation in patients with AEH.

Pre-operative identification of factors that may help to stratify a patient's risk of concurrent EC is mandatory to reduce the risk of over- or under-treatment.

Our study aims at evaluating the presence of pre-operative clinical, ultrasonographic, hysteroscopic, and anatomopathological features in patients with a hysteroscopic diagnosis of AEH and a postoperative diagnosis of EC.
