Colon cancer or colorectal cancer often begins as a benign growth known as a colon polyp. After the disease begins to spread, it can produce signs and symptoms like. 1  blood in the stool, 2  changes in bowel patterns (like diarrhea or constipation), 3  abdominal pain,4  weight loss, or. 5  fatigue.olon cancer or colorectal cancer often begins as a benign growth known as a colon polyp. After the disease begins to spread, it can produce signs and symptoms like. 1  blood in the stool, 2  changes in bowel patterns (like diarrhea or constipation), 3  abdominal pain,