Objective This study aimed to analyze long-term survival of clear cells (CCs) and endometrioid (E) ovarian cancer cases according to presence of endometriosis in the pathologic report.

Methods This is a retrospective analysis of 47 CC and 66 E ovarian cancer cases observed consecutively at our center between 1990 and 2010.

All cases had first surgery at our center or were referred to it for treatment and follow-up.

Cases were identified according to the original diagnosis reported in clinical records.

All pathologic reports were reviewed, and cases were classified with or without pathologic evidence of endometriosis on the basis of the pathologic report.

Follow-up was updated in March 2011. The follow-up median was 147 months (range, 116–171).

Results Endometriosis-associated ovarian cancer cases were more frequently diagnosed at stage I to II than cases without endometriosis: among the 36 endometriosis-associated ovarian cancer cases, 25 (69%) were at stage I or II, and the corresponding value was 35 (46%) of 77 among cases without endometriosis (P = 0.0173).

The presence of endometriosis tended to be associated with a higher 10-year survival rate: after taking the potential confounding effect of stage into account, the finding was not statistically significant (hazards ratio, 0.7; 95% confidence interval, 0.3–1.5).

Conclusions This analysis shows that EA CCs and E ovarian cases are diagnosed at an earlier stage than cases without endometriosis. No clear association emerged between presence of endometriosis and survival.