Ugh! I've been in your shoes. I know all too well how fear takes over! And trust me, it can consume us and make for bad and rash decisions. Gynecologic surgeries are way overused. These include hysterectomy (uterus removal), oophorectomy (ovary removal), cyst removals, and c-section. They are big money makers for surgeons, anesthesiologists, hospitals.
Ovarian cancer is rare for women without a family history. Less than 2% of women get it (1.3% per SEER statistics). Ovarian cysts are very common and most are benign, even complex ones. And most resolve on their own. However, being that yours is 7cm, it may not go away. Since this is a "solid mass" it could even be hemorrhagic (blood filled) since those appear solid on imaging. And hemorrhagic cysts go away on their own although they can grow before resolving. It would be a real shame to go through surgery if it wasn't necessary especially if they remove your ovary.
This site is very informative - http://ovaryresearch.com/ovarian_cysts.htm. It talks about the various types of cysts and the fact that surgeons with good cystectomy skills can almost always remove just the cyst keeping the ovary intact. The non-profit HERS Foundation also has some info on their site about ovarian cysts.
Not only is preservation of the ovary important for fertility, the ovaries produce health promoting hormones a woman's whole life. Removal of even one ovary has been shown to increase risk for some health problems such as cognitive impairment, dementia and parkinsonism.
Have you gotten multiple opinions and ones from doctors in different networks (e.g. affiliated with different physician groups and hospitals)? Have you gotten a copy of your medical records especially the imaging report that describes the cyst? If so, do you want to share what it says about the cyst's characteristics?
What have you been told about details of the surgery besides that it will be a laparotomy? Some surgeons do not offer laparoscopic because they don't have those skills. Now if the cyst has a "good" chance of being malignant, laparotomy is normally done. But again, if there's no family history, cancer is unlikely. And what were you told about removal of the cyst versus ovary and any other organs? Women seldom are provided with all these details. Regardless of what you are told, you will want to revise the surgical consent form to make your wishes explicit and have the surgeon sign off on your revisions. For instance, if the cyst is benign (based on the frozen section done while you're in the OR), only the cyst should be removed. All organs should be left intact. Complete the consent form and secure surgeon's sign-offs days before surgery. That way if the surgeon is not "on the same page" you can cancel.
I wish I had known much more than I did 12 years ago when my sex organs were unnecessarily removed.
I hope this helps! I know it's hard to think clearly through all this but it's important. And don't let anyone rush you into it. If will be happy to share more if you have questions.