Early detection is your best defense against cancer. Cancer can cause a variety of symptoms, depending on the site of the disease. Recognizing the symptoms and knowing when to seek treatment can save your life. Notify your doctor immediately if you experience any of the following seven cancer warning signs, as identified by the American Cancer Society: 1. Changes in bowel or bladder habits -- Diarrhea, constipation, or narrowing of the stool that lasts for more than a few days or any rectal bleeding or blood in the stool can be symptoms of colorectal cancer. Changes in bladder habits, including frequent urination or feeling as if you need to go but not being able to urinate, or any blood in the urine may be symptoms of bladder cancer. But, there may be other causes for these problems, so see your doctor for evaluation. 2. Sores that don't heal -- The most common sign of skin cancer is a change on the skin, such as a growth or a sore that won't heal. Sometimes there may be a small lump. This lump can be smooth, shiny and waxy looking, or it can be red or reddish brown. Skin cancer may also appear as a flat red spot that is rough or scaly. Not all changes in the skin are cancerous, but a doctor should be seen if changes in the skin are noticed. 3. Obvious changes in a mole or wart --Spots on the skin that change in size, shape, or