Stool Shape
Narrow or thin stools, which look similar to a pencil or ribbon, might be a possible symptom of bowel cancer. This unusual stool shape can be triggered when the colon is narrowed as cancerous cells develop and block the colon. You can think of the bowel as a hollow tube. When a tumor grows inside this area, it would begin to restrict the flow of your stools. Make sure to consult your doctor as soon as possible as this is a very typical sign. [2]