Objective The aim of this study was to analyze and compare the clinicopathologic features and prognosis of clear cell ovarian carcinoma (CCOC) and endometrioid ovarian carcinoma (EOC) associated or not with endometriosis.

Methods This was a reconstituted cohort study from a single-institution Brazilian cancer center approved under review board no. 68150617.7.0000.5404 with 50 patients with CCOC and EOC diagnosed between 1995 and 2016, followed up until 2017. Clinicopathologic characteristics and survival outcomes were analyzed.

Result(s) There were 23 women (46%) with CCOC and 27 with EOC (54%); 80% of those women had histologic confirmation of endometriosis; 42% were nulliparous, and 42% were premenopausal; and cancer antigen 125 was elevated in both International Federation of Gynecology and Obstetrics stages I–II disease (mean, 614.7 Ui/mL; range, 3–6030 Ui/mL) or International Federation of Gynecology and Obstetrics stages III–IV disease (mean, 2361.2 Ui/mL; range, 8–12771 Ui/mL). Women with EOC were 7 years younger than those with CCOC. When associated with endometriosis, CCOCs were more likely diagnosed at earlier stages. Endometrioid ovarian carcinoma and CCOC at initial stage and EOC at advanced stage share similar good prognosis. Univariate analysis showed that CCOC not associated with endometriosis has worse overall survival (OS). However, multivariate analysis showed that only abnormally elevated levels of cancer antigen 125 and advanced stage at diagnosis were significantly associated with reduced progression-free survival. Tumor stage remains the only prognostic factor for OS.

Conclusions The presence of coexisting endometriosis did not change the prognosis of EOC but was associated with better OS in patients with CCOC. Patients with CCOC and EOC at initial stages and EOC at advanced stages have a good prognosis; however, CCOC at advanced stages had a sooner recurrence and shorter OS.