Introduction Endometrioid carcinoma of ovary (ENCO) and clear cell carcinoma of ovary (CCCO) are rare, accounting for < 20% of all ovarian malignancies with a small subset arising in the background of endometrioses. The aim of this study was to analyze the clinico-pathological factors, survival outcomes and prognostic factors for survival in patients treated with ENCO and CCCO.

Methods All consecutive patients diagnosed with ENCO and CCCO between January 2014 to December 2020 were included for this single institution retrospective study. Data was retrieved from the electronic medical records. Time to event data were analyzed using the Kaplan-Meier method. Log rank test and cox regression analysis were used to analyze the effect of different variables on survival.

Results Total 295 patients were included out of which 49.5% (n=146) had CCCO and 50.5% (n=149) had ENCO. Forty-two (14.2%) had associated endometrioses. FIGO stage IC was the most common, 36.9% (n=109) followed by stage IA, 27.8% (n=82). Out of 290 patients who underwent surgery, 78.6% (n=228/290) underwent R0 resection. Median duration of follow up was 54 months (range 47–60 months). The 5-year progression free survival (PFS) was 59% and 5-year overall survival (OS) was 67%. Multivariate analysis showed residual disease, clear cell histopathology and advanced stage were significantly associated with shorter PFS and OS.

Conclusions Presence of macroscopic residual disease, clear cell histopathology and FIGO stage III - IV were significantly associated with higher risk of relapse and death. Co existent endometrioses was not associated with a better prognosis in any stage.