Prognostic Value of Peritoneal Cytology in Stage I Serous and Clear Cell Carcinoma of the Endometrium.

(1) Background: To investigate the relation between malignant peritoneal cytology and survival outcomes in patients who underwent primary staging surgery for stage I uterine serous (USC) or clear cell carcinoma (UCCC). (2) Methods: In this retrospective analysis, patients with stage I USC or UCCC who underwent staging surgery between 2010 and 2020 at the Peking Union Medical College Hospital were identified and reviewed. (3) Results: A total of 101 patients were included, and 11 patients had malignant cytology (10.9%). The median follow-up time was 44 months (range 6-120) with a total of 11 (10.9%) recurrences. Patients with malignant cytology had a higher likelihood of peritoneal recurrence and a shorter time to relapse (13 vs. 38 months, p = 0.022), as compared to patients with negative cytology. In univariate analysis, malignant cytology and serous histology had worse progression-free survival (PFS) and overall survival (OS) (all, p < 0.05). In sensitive analysis, the detrimental effects of malignant cytology on survival were more prominent in patients over 60 years old, those with serous histology, stage IB disease, and those who received hysteroscopy as a diagnostic test. (4) Conclusions: Stage I USC or UCCC patients with malignant peritoneal cytology had a higher recurrence and inferior survival.