VERY FEW ovarian cysts, including complex ones, are cancerous. Per U.S. government stats, a woman's lifetime risk of ovarian cancer is less than 2% (1.3% to be exact). Cysts are common and usually resolve on their own in 3 months or so. Imaging is not exact so although it may appear complex, it may be some other type of cyst.
Unfortunately, FAR too many women lose an ovary(ies) for benign ovarian cysts. If future imaging shows that the cyst is growing, a good surgeon should be able to remove just the cyst preserving the ovary or enough of it for hormone production. This is discussed here- http://ovaryresearch.com/ovarian_cysts.htm. There's a lot of other good info on this ovaryresearch site.
The ovaries are essential to good health our whole lives. After menopause, they continue producing hormones with increasing levels of testosterone (T) that reach reproductive levels in a woman's 70's and remain stable thereafter. Some of this T is converted into estrogen as needed by the body. Removal of one ovary (or the uterus or tubes) can permanently disrupt the endocrine system increasing risk for many health problems.
My gynecologist was dishonest when I developed a complex cyst and he removed all my parts (uterus, both ovaries and tubes) even though the frozen section done while I was in the operating room was benign. The vital functions of the ovaries and uterus became apparent very quickly! It's been 11 years since my surgery and I wish I knew just a smidgen of what I know now.
Best of luck to you and please post back as you get more info.