Apparently women who have ovarian cancer are 8 times as likely to have hypodontia (congenitally missing teeth) than those without ovarian cancer.
The absolute rates aren't small either...20% of women with epithelial ovarian cancer have hypodontia, as opposed to 3% of women overall. Women are 4 times as likely to have hypodontia as men.
I bring this up because I think it's an interesting clear case of correlation without causation. Missing teeth don't cause ovarian cancer, and ovarian cancer doesn't cause missing teeth. It's also an interesting case of how research has to move in two directions. Now that there's proof that ovarian cancer patients tend to have hypodontia, there are trials underway to see if women with hypodontia get ovarian cancer, and if so how high the rate is. A correlation also does not mean prediction. Prediction means prediction.
If you're wondering why this came up, it's because I have hypodontia, and I'd never really thought to look it up until now*. Apparently it's a half decent idea for me to let my primary care doctor know about this, as there are very few early signs of ovarian cancer. Science....it never fails to surprise me.**
*Sometimes I forget we have the internet. Not really, but sometimes there are questions I had pre-internet that it never occurs to me I can get answers to now. I found out about the teeth thing when my teeth failed to develop, back in around 1993 or so.
**In case you're really curious about my dentistry: I'm congenitally missing 8 teeth total, but 4 of them are my wisdom teeth. To be clear, these were not pulled, they never existed. Wisdom teeth (third molars) don't count in the diagnosing of hypodontia. I'm completely missing my mandibular second molars, and I only have baby teeth for my mandibular second bicuspid (second premolar). None of this is visible unless you're seriously looking in my mouth, but dentists do generally go "oh cool!" when they see my mouth for the first time. The teeth I'm missing are all the most common ones, though 4 is on the high side to be missing (all the people in the study were only missing one or two). I also had a tooth try to grow in on the roof of my mouth, but that's a whole different story.