A prospective cohort study at a Tertiary University Hospital. From January to December 2018, we enrolled women with the following criteria: abnormal uterine bleeding in post-menopause, endometrial thickening in pre-or post-menopause; tamoxifen usage. Patients underwent office hysteroscopy with a 5-mm continuous-flow hysteroscope and endometrial biopsies were taken using miniaturized instruments. Senior operators had to foresee histopathological diagnosis using a questionnaire. Histopathological examination was conducted to confirm the diagnosis.

Patient underwent the procedure after the menstrual phase (day 6 to 10) of a spontaneous menstrual cycle. All the procedures were performed by means of a continuous flow small-diameter hysteroscope with oval profile (maximum diameter 5 mm, minimum diameter 3.9 mm) (Bettocchi Office Hysteroscope size 5, Karl Storz GmbH & Co., Tuttlingen, Germany) fitted with a 30-degree telescope of 2.9 mm gauge, using the vaginoscopic approach, without tenaculum and speculum, and using saline solution as distending medium at 90-100 mmHg pressure generated by a pneumatic cuff and measured by means of a manometer; the biopsies were performed with the "punch" or "grasp" technique using a 5 Fr grasping forceps inserted through the operating channel of the hysteroscope. In case of small intrauterine pathologies, they were easily removed by means of a straight bipolar electrode active by an electrosurgical generator (Versapoint II; Gynecare, Ethicon) used to provide a 50W power for the mildest vapour cutting mode (VC3).

The hysteroscopic diagnosis of hyperplasia was based on one or more of the following findings: (1) focal or diffuse, papillary or polypoid, endometrial thickening, (2) Abnormal vascular patterns; (3) evidence of glandular cysts; (4) abnormal architecture features of glandular outlets (thickening, irregular gland density, dilatation). Although no consensus or RCTs showed agreement in describing objective criteria for EH, several trials agreed on the previous morphologic evaluation. [8].

The procedures were taken by three senior gynaecologists (P.D.F, L.C., N.C) whose expertise and skills were equivalent. After every procedure, surgeons were asked to propose a suggestive histological categorization of the clinical diagnosis by means of a questionnaire, in order to standardize the assessment. The questionnaire was made of a progressive number which identified the biopsy and a multiple-choice question. Operators were asked to choose one from the following answers: Benign (including atrophic endometrium, proliferative endometrium, endometrial polyp/s); Endometrial Hyperplasia (simple or complex hyperplasia); Atypical Hyperplasia/Carcinoma (including atypical endometrial hyperplasia and adenocarcinoma) Biopsied histological samples were sent for histopathological analysis. The histopathological examination of all the specimens was performed at the Pathology Unit of University of Campania "Luigi Vanvitelli". Three senior gynecopathologists (INS), with the same skills and expertise, were addressed to evaluate all the biopsies

Inclusion Criteria:

• abnormal uterine bleeding in post-menopause
• ultrasonographic detection of endometrial thickening in pre-menopause
• ultrasonographic detection of endometrial thickening in post-menopause
• follow-up after Tamoxifen-based therapy regimens

Exclusion Criteria:

• severe urinary symptoms
• history of severe comorbidities (autoimmune disorders, chronic diseases and severe cardiac disease)

Women included in this study are referred by gynaecologists of the general outpatient rooms of the institution's hospital