They say if your hand is bigger than your face you have a tumor. I believe the test first came into practice in the late 1750's, somewhere in Eastern Europe. I'm not sure about the exact position you have to hold your hand in, but I hear it's a pretty reliable test if you do it right.
If you don't do anything about it, really anything could happen. Tumors are like the wizards of the body. They can do all sorts of horrible things, or nothing. You should ask a trained medical professional. Or a consultant for a medical drama TV show. I would try to get House's or Scrubs'. Only use Grey's Anatomy's as a last resort.