I'm a bit of a hypochondriac. Specifically, I think that basically any unusual or unexpected ache, pain or swelling is cancer. Fortunately, for my doctor especially, I am usually pretty good at deciphering which symptoms actually need to be checked out and which are likely just random and normal body fluctuations.
There are symptoms, however, that according to the Mayo Clinic should not be ignored. For example, if you lose 5% of your body weight within a month or 10% in 6 to 12 months and you can't explain why, you should have a chat with your family doctor. Unexplained weight loss can be an indicator of a range of conditions including cancer, liver disease and depression.
If you've injured a joint and it has become hot, red and/or swollen, you need to seek help as you may have a joint infection that could eventually lead to the loss of a limb. Other warning signs you should never ignore include shortness of breath, severe headaches, flashes of light and feeling super full when you've hardly eaten anything. To see the rest of the symptoms as well as the reasoning behind why you need to get then all checked out, take a look here.