My little sister found out she has ovarian cysts. are they harmful?

Probably not: For women who are still in their reproductive age range, and not on some form of hormonal suppression (birth control), the normal job of the ovaries is to produce eggs every month, and the eggs develop in cysts. So, many ovarian cysts are normal, functional (healthy-even!). If one has pain and a larger than 'normal' cyst is found, or if it is 'complex'-f/u sono &labs can check if it may b harmful.