Increased association of ovarian cancer in women with histological proven endosalpingiosis

Background: Few studies have investigated the possible association between endosalpingiosis and ovarian cancer, therefore we assessed whether there is an association between histological confirmed endosalpingiosis and ovarian cancer. Methods: We identified all women with a histological diagnosis of endosalpingiosis between 1990 and 2015 from the Dutch nationwide registry of histopathology and cytopathology (PALGA). We used women with a benign dermal nevus as controls. Histology results for cancer of the ovaries, fallopian tubes and peritoneum between January 1990 and July 2017 were retrieved. Incidence rate ratios (IRR) were estimated for ovarian cancer and its subtypes. Results: We found 2490 women with a histological diagnosis of endosalpingiosis, of which 1005 women 40.4 %) had concurrent endometriosis. The age-adjusted IRR for ovarian cancer in endosalpingiosis patients (including endometriosis) was 43.7 (95 %CI 35.1-54.3). Excluding cases with concurrent endometriosis, resulted in an age-adjusted IRR of 38.8 (95 %CI 29.3-50.4). IRRs were 2.4 (95 %CI 1.4-3.9) and 1.8 (95 %CI 0.8-4.0) respectively when excluding synchronously diagnosed cases. The increased IRRs seem to be caused by an increased risk of clear cell and endometrioid ovarian cancer subtypes. Conclusions: This study shows an association between histological diagnosed endosalpingiosis and ovarian cancer. The association with endometrioid and clear cell subtypes seems most outspoken. Additionally, this study shows that this association is independent of histological endometriosis diagnosis, making it important for pathologists to report endosalpingiosis accurately and for gynaecologists to be more aware of the increased association of ovarian cancer in women with endosalpingiosis.