Polycystic ovary syndrome [PCOS] is the most common endocrinopathy of women in reproductive age. An association between PCOS and type-1 endometrial cancer has often been reported in the literature. The prolonged anovulation with consequent continued secretion of estrogen unopposed by progesterone may enhance the development and growth of this malignancy, particularly in young women. Hypersecretion of luteinizing hormone [LH], chronic hyperinsulinemia and increased serum insulin-like growth factor [IGF]-I levels may represent risk factors for endometrial cancer. However, data available in the literature do not allow a meta-analysis to be carried out to calculate an estimate of the relative risk of endometrial cancer in women with PCOS. Anecdotal cases of low-grade endometrial stromal sarcoma and carcinosarcoma have been reported in association with prolonged unopposed estrogen stimulation, and in particular with PCOS. A few studies have addressed the possibility of an association between PCOS and epithelial ovarian cancer risk, and the results are conflicting but generally reassuring, and similarly the few available data appear to exclude a strong association between PCOS and breast cancer.