Ovarian Cysts in Post-Menopausal Women

I have read your past Q&A on this subject and understand that ovarian cysts are not cancer and do not generally become cancer.  However, I have also read in other literature that "an ovarian cyst in a post-menopausal woman is also frequently malignant."  In another place I read that in post-menopausal women "10% of ovarian cysts are functional cysts and 90% are tumors, either benign or malignant."  I am 54 years old and have just discovered that I have an ovarian cyst.  I think my doctor is doing the right things but I am just a bit confused about these seemingly contradictory things that I am reading.  In a post-menopausal woman, can an ovarian cyst be a cyst caused by ovulation?  Can a tumor masquerade as a cyst?  Any help would be greatly appreciated.