In medicine, cancer is a malignant tumor that originates from epithelial tissue and is the most common type of malignant tumor. Among tumors, malignant tumors originating from mesenchymal tissues we call sarcomas. What people call cancer customarily refers to malignant tumors in general. The incidence of malignant tumors is relatively high nowadays, except for the scalp and nails where there are no tumors, malignant tumors occur in almost all parts of the body. Based on the fact that there is no clear cause of cancer, it is more difficult to prevent cancer. What we can do now is to improve our own defense and disease resistance, maintain good living habits, early detection and early treatment. By early detection and early treatment, we mean that patients should have regular medical checkups so that if there are any adverse symptoms or precursors of cancer, they can be seen and detected in time. Although cancer is terrible, many cancers can be cured by early treatment if they can be diagnosed and treated early.