In all the years I have been treating my own animals for cysts I have not lost one through stress or post operative infections. I can also speak for many other owners I know who have undertaken this simple work. By treating early, only a small wound is made so is less liable to become infected. If cysts are left to grow, eventually they will burst open and there will be a huge crater which obviously is more likely to become infected. There is no other option than to have all the debris that is commonly found in large cysts, removed under local anaesthetic and the wound sutured.
Ovarian Cysts can grow up to the size of a golf ball and still cause the animal no discomfort.
One of the side effects of them, however, is that it makes the sows hyper active when they are in season.