Design: This retrospective study included all patients who were diagnosed with uterine malignancies and underwent surgical staging between 2016 and 2022. We compared positive cytology rates with regards to preliminary diagnostic methods

Setting: A single, university-affiliated, tertiary medical center

Patients or Participants: The study included 305 patients with uterine malignancies who underwent surgical staging ,of which 259 had molecular assessment for MMR proteins. We compared the rate of positive cytology between women in whom tissue diagnosis was acquired by hysteroscopy (study group) to those initially diagnosed by uterine curettage or low-pressure endometrial suction sampling (control group).

Interventions: N/A

Measurements and Main Results: During the trial period, 215 patients had cytology obtained ,of whom 40 were diagnosed with positive cytology (19%). There was no significant difference in positive cytology rates between patients that underwent prior hysteroscopy and controls (11% vs 13%, p=0.1).Logistic regression adjusting for histological tumor type, stage and MMR deficiency showed no significant difference in positive cytology for patients that underwent hysteroscopy prior to surgery (aOR 0.493 CI95% 0.22-1.1). Of all surgically staged patients 60 (23%) were diagnosed with MMR deficiency. Adjusting for age, tumor type and specific MMR deficiency – in MLH1& PMS1 deficient tumors, hysteroscopy was shown to be a protective factor for positive cytology (aOR 0.44 CI95% 0.21-0.98)

Conclusion: This study suggests that preoperative hysteroscopy does not pose a risk factor for dissemination of endometrial cancer cells with regards to MMR protein status in women with uterine malignancies. Moreover, in MLH1& PMS1 protein deficient tumors, hysteroscopy was shown to be a protective factor for positive cytology. Further studies are needed to confirm this finding and investigate the underlying mechanisms before information can be used in clinical settings.