The determination of the degree of differentiation of lung cancer refers to the degree of similarity of the lesion to the source tissue under the microscope. The degree of differentiation of lung cancer is able to assess the degree of malignancy of the lesion, and depending on the different degrees of differentiation, there are some differences in treatment options and prognosis. There are 4 grades of differentiation, with grade 1 being the most similar to the tissue of origin and the least malignant, and grade 4 being undifferentiated carcinoma, which is the most different from the tissue of origin and the most malignant. The lower the grade, the better the surgical result, because the cells have less ability to recur and metastasize, and can be easily removed completely. The higher the grade, the higher the degree of malignancy, and although it is more sensitive to chemotherapy and radiotherapy, it is easy to produce drug resistance due to its strong dividing ability, and the overall effect is poorer.