The tumors are divided into benign and malignant. Benign tumors usually grow slowly. They usually do not recur or rarely recur after resection, and they do not metastasize. They are relatively close to normal cells and tissues in shape; malignant tumors usually grow faster. , There will often be recurrence and metastasis, and there is obvious atypia. In general, malignant tumors can cause serious harm to the human body.

　　However, if a benign tumor grows in Certain critical parts (such as the brain) or the secretion of too many abnormal substances can also have serious consequences, and even life-threatening should be paid attention to. The benign and malignant tumors are sometimes not clear. Some benign tumors have a higher local recurrence rate, and some will gradually transform into malignant tumors.

　　 Therefore, objectively there is a group of borderline tumors. There are also cases where malignant tumors change to benign, but they are extremely rare.

　　 People usually refer to malignant tumors as cancer. Almost all human organs and tissues may develop cancer, but strictly speaking, cancer refers to a type of malignant tumor that originates in epithelial tissue, such as liver cancer, breast cancer, skin cancer, etc., accounting for about 90% of malignant tumors. In addition, 10％ malignant tumors originating from mesenchymal (non-epithelial) tissues such as bone, muscle, and blood vessels are collectively called sarcomas, such as lymphoma and rhabdomyosarcoma are malignant tumors originating from lymph and striated muscle cells.