Most women will have an ovarian cyst at some point in their lives, though most will never know it. A majority of ovarian cysts are harmless (non-cancerous) and go away on their own. You often never experience any discomfort. However, you will have serious symptoms if the ovarian cyst ruptures.
For women under 50, ovarian cysts are almost never cancerous.
If you have an ovarian cyst, you probably won’t know it until after a routine pelvic exam. (On the other hand, if the cyst ruptures, then you will definitely know about it.)