Is pulling black shit cancer?

Black stools are not necessarily cancer.

Black stools are mostly formed due to oxidation of blood in stools. When patients eat pork liver, duck blood and other foods, the color of stools may change. When patients develop gastritis, esophageal or gastric varices, gastric ulcers and other diseases, it may cause upper gastrointestinal bleeding, resulting in black stools. If the patient has gastric cancer, the cancer cells invade the gastric mucosa and surrounding tissues, which can cause local rupture and bleeding, and the patient can also show black stool color.