Narrow stools
This is often a late symptom of colon cancer because it requires the tumor to be large enough to cause a serious alteration to the intestinal lumen. Cancer usually grows to the inside of the colon, and as it grows it would reduce the available space for stools to move through the intestines. When the malignant tumor is very large, it would leave a small area in the intestinal lumen for the stools to pass, and by trying to fit in place, we will get narrow stools.