"Of course, there's no simple way to tell whether your headache is a brain tumor, but doctors do have some red flags. Before reading them, there are some important points to remember. First, 50%-60% of all people with brain tumors don't have headaches at all, Barnett says. Second, your headaches could fall into all these red flag categories and you could not have cancer. Third, your headaches could fall into none of these categories and you could still have a brain tumor."
Fourth, if you get headaches, it might or might not be cancer. But even if you don't have headaches, you could have cancer anyway. Although, not necessarily.
Hope this helps!
ps- Don't. Panic.