Risk factors for different histological types of ovarian cancer.

Various histological types of ovarian cancer may develop from different etiological aspects. Data separated by histological subtypes collected in the framework of a large case-control study on ovarian cancer conducted in Italy were analyzed. The cases were women below the age of 75 years, admitted to a network of hospitals in Milan. Cases were grouped into four categories by histological type: mucinous tumor (n = 52), serous tumor (n = 680), endometrioid tumor (n = 41), and other histologies including clear-cell and undifferentiated epithelial tumors (n = 50). Controls were 2758 patients admitted to the same network of hospitals for a wide spectrum of acute, nongynecological, non-hormone-related, non-neoplastic conditions. In comparison with nulliparae, the risk of serous, endometrioid, and other histologies of ovarian cancer tended to be lower in parous women, but the odds ratios (OR) were above unity for mucinous ovarian cancer. Oral contraceptive use was associated with OR lower than unity for serous (OR = 0.7) and endometrioid (OR = 0.8) ovarian cancers but not for mucinous (OR = 1.4) and other histologies (OR = 1.6). Finally, our results on dietary fat intake did not show substantial differences in all histological types of ovarian cancer.