Tumor classification is the process of categorizing tumors based on their characteristics, such as cell type, location, and behavior. Tumors can be classified as benign, which are non-cancerous and do not spread, or malignant, which are cancerous and can invade nearby tissues and metastasize to other parts of the body. There are several systems for tumor classification, including the TNM system, which assesses tumor size (T), lymph node involvement (N), and metastasis (M). Additionally, tumors can be classified by their histological type, such as carcinomas, sarcomas, or lymphomas, which helps guide treatment decisions and prognosis.