There is not a normal tumor marker number, according to the National Cancer Institute. Noncancerous conditions can sometimes cause tumor markers to rise. Markers have not been identified for every type of cancer, and some people with certain types of cancer do not experience higher marker levels.
Cancer cannot be diagnosed by an elevated tumor marker alone, explains the National Cancer Institute. Tumor markers are combined with other tests, such as biopsies, to determine a cancer diagnosis. Tumor markers are also sometimes used during cancer treatment since a drop in levels could indicate the treatment is working. Tumor markers are measured using a sample of tissue or body fluid.