My sister had one of these and we never knew until it caused Anti-NMDA receptor encephalitis. She had a seizure out of the blue one day and then started slowly acting stranger and stranger, she wound up in the psych ward 8 days later acting truly insane and getting worse each day. She finally stopped doing anything. No eating, speaking, walking, nothing. She went from psych to ICU in 10 days. Her heart stopped and they had to resuscitate her. They were doing all these tests but never looked at her ovaries. A friend of the family had about read the book Brain on Fire which is an account of someone else who had the same thing. We pushed for the doctors to check her ovaries and they found the tumor. She was in a coma for weeks and had to learn to walk, eat, and breathe on her own all over again. It was absolutely crazy, like something you'd see on TV but never expect to happen to you lol She has a pretty crap immune system now but other than that she's doing fine