Tumor grading refers to determining the degree of malignancy of a tumor based on pathomorphological indicators such as the degree of differentiation, heterogeneity, nuclear schizophrenia and the type of tumor. The specific grading of different tumors is also different, some are divided into three grades, and some tumors are divided into four grades. In general, most tumors are divided into grades 1-4, which are indicated by G1, G2, G3 and G4 respectively. G1: Tumor cells and tissues that look most like healthy cells and tissues are called well-differentiated tumors. The tumor is considered low-grade and has a low degree of malignancy. G2: Tumor cells and tissues are somewhat abnormal, do not look like normal cells and tissues, and grow faster than normal cells, called moderately differentiated tumors. The tumor is considered intermediate grade and relatively malignant. G3: Tumor cells and tissues look very abnormal and are called poorly differentiated tumors. The tumor is considered high grade and more malignant. G4: Tumor cells and tissues look most abnormal and are called undifferentiated tumors. These tumors are considered the highest grade, the most malignant, and grow and spread more rapidly. There is also a special grade, GX, which indicates that the doctor is unable to assess the grade, also known as an undetermined grade. The grading of a tumor determines the degree of malignancy and provides a basis for clinical treatment and prognosis.