Introduction/Background Selection of the patient who is suitable for a fertility-preserving approach (FPA) is extremely important. This study aimed to reveal the molecular characteristics of cases in which FPA was applied.

Methodology Sixteen endometrial cancer (EC) cases were evaluated according to the Proactive Molecular Risk Classifier for Endometrial Cancer (ProMisE) molecular classification. Mismatch repair-deficient (MMRd) and p53abn were evaluated by IHC, and POLE exonuclease domain mutations (POLEmut) by Sanger sequencing. The relationship between clinical-pathological prognostic factors and molecular features was analyzed.

Results The mean age of our cases was determined as 32.6±5.0 (25–40) and the mean BMI was 32.2±6.9 (22–46). One case was diagnosed with hyperplasia with atypia, and the others had grade 1 endometrioid adenocarcinoma. As a diagnostic method, hysteroscopy was performed in 2 cases and D&C was performed in 14 cases. Squamous metaplasia was detected in 6 cases.The type of progesterone used in the treatment was megestrol asetat in 11 (68%) patients and megestrol asetat+LNG IUD in 5 cases. Complete remission occurred in 6 (38%) of our cases. A total of 4 pregnancies and 3 live births were achieved. Three relapses were observed in patients. Laparoscopic BSO was performed due to ovarian metastasis in a case who underwent hysterectomy after two births. Endometrial recurrence developed during follow-up in the other 2 cases. In total, hysterectomy was performed in 12 cases, and hysterectomy +BSO was performed in 7 (58%) cases. The median follow-up period was 58.0 (3–151) months.

Conclusion Except for one of our cases, all of them were in the NSMP group. They show very different characteristics and treatment responses. There is a need for further study on other molecular features that can predict prognosis and treatment response in the NSMP group. Response rates to progesterone treatment in cases with squamous metaplasia should also be evaluated in larger series.

Disclosures None.