Colon cancer does not always present symptoms in the early stages.
Colon cancer symptoms usually do not appear until the disease has
progressed into an advanced stage. This makes screening highly valuable
-- it can detect colon cancer in the early stages, before symptoms begin
to appear.
Blood in the Stool
Blood in the stool is a common symptom of colon cancer, but you can't always actually see blood that may be in the stool. Tests like the fecal occult blood test (FOBT) detect blood that may be unseen to the naked eye. It is also associated with less-severe health problems, such as hemorrhoids and anal fissures.
http://cancer.about.com/od/coloncancer/p/colonsymptoms.htm
Blood in the Stool
Blood in the stool is a common symptom of colon cancer, but you can't always actually see blood that may be in the stool. Tests like the fecal occult blood test (FOBT) detect blood that may be unseen to the naked eye. It is also associated with less-severe health problems, such as hemorrhoids and anal fissures.
http://cancer.about.com/od/coloncancer/p/colonsymptoms.htm