According to the characteristics of tumor cell morphology and the different effects of tumors on the structure and function of human organs, tumors are divided into two types: benign and malignant. The treatment and prognosis of these two types of tumors are completely different. Therefore, it is important to distinguish which type they belong to for proper diagnosis and treatment. From the word meaning of benign and malignant, we can understand that benign is also good, which means that this kind of tumor is good in nature and not harmful to people. However, malignant means vicious and bad. The malignant tumor is a serious threat or danger to human life. These two types of tumors are determined by the nature of the tumor cells. A benign tumor is an abnormal proliferation of some tissues, forming a lump that gradually increases and expands and grows, which can compress the organ and affect its function. For example, benign tumor in bronchus may block the lumen of trachea after enlargement. Eventually, the lung cannot expand, resulting in shortness of breath and difficulty in breathing. Benign tumors do not produce tumor metastasis. Malignant tumors, on the contrary, grow rapidly. They grow mainly in an infiltrative manner and can metastasize tumor cells to other tissues and organs in the body with the help of lymphatic tracts, blood channels or luminal tracts. The shape and size of tumor cells, the characteristics of nucleus and the surrounding invasion and metastasis of tumor can be observed by microscope. The diagnosis can be determined. Malignant tumor cells also have metabolic characteristics. The synthesis of nucleic acid increases in malignant tumors, the synthesis of protein is greater than the breakdown, glycolysis increases, and human nutrition is consumed by tumors, causing cachexia in patients.