Clinically, there is no such thing as where there is cancer in the body, there will be blackness. Different cancers have different clinical manifestations, so not all cancers will lead to blackening of certain parts of the body or secretions, but some cancers do lead to blackening of different parts of the body or secretions, for example, liver cancer patients may have blackened face; oral cancer patients may have blackened teeth; melanoma patients may have blackened skin; stomach cancer and intestinal cancer patients may have blackened stools. Patients with intestinal cancer may have black stool. 1. Black face: The early symptoms of liver cancer patients are usually not obvious, and when they have black face, the disease has generally entered the middle and late stages. The black face of liver cancer patients is caused by bile duct obstruction due to tumor invasion, or jaundice caused by combined cirrhosis or chronic hepatitis, with the deposition of bilirubin, the patient’s skin color will gradually change from yellow to black, and the black face will appear; 2. These people often have black teeth because of the above chemical stimulation and poor hygiene habits, and such repeated chronic stimulation is the factor that triggers oral cancer. Patients with oral cancer often have blackened teeth and oral mucosa lesions, such as hard nodules and ulcers, as well as loose teeth and difficulty in opening mouth; 3. Blackened skin: melanoma is a malignant tumor with high malignancy, which originates from melanocytes. Melanoma cells can appear on the skin surface, oral mucosa and nails, and the lesions can be black, blue-black or brown pigmented plaques or nodular changes, which can form ulcers; 4. Black stool: When gastric cancer or intestinal cancer occurs, due to the cancerous digestive tract mucosa erosion and bleeding, blood stays in the intestine for a long time, and the bacteria in the intestine decompose hemoglobin, which, under the action of gastric acid, synthesizes iron sulfide with the intestinal The bacteria in the intestine decompose the hemoglobin and, under the action of gastric acid, synthesize iron sulfide with the sulfide in the intestine, which mixes with feces and makes the stool black. The early symptoms of stomach cancer can be easily confused with common stomach diseases, such as gastrointestinal and stomach pain. Bowel cancer may also show changes in bowel habits, changes in stool characteristics, or even abdominal masses or acute intestinal obstruction. No matter which of the above symptoms appear, screening gastroscopy is needed to detect early gastrointestinal lesions in time. However, it should be noted that it is not the case that black face, black teeth, black patches of skin or black stool indicate cancer in the body. Generally, cancer patients will have other discomforts, such as weight loss, loss of appetite, severe pain, etc. Therefore, when certain parts of the body or secretions are black, they can go to regular hospitals for examination. It is also necessary to do regular medical checkups in daily life to facilitate early screening of diseases.