Cervical intraepithelial neoplasia is classified into 3 grades: Grade I: Mild atypical hyperplasia. The nuclei of the lower third of the epithelial layer are enlarged, the nucleoplasmic ratio is slightly increased, the nuclear staining is slightly deepened, the nuclear division phase is less, and the cell polarity is normal. Grade II: i.e. moderate atypical hyperplasia. The nuclei of the subepithelial one-third to two-thirds layer of cells were obviously enlarged, the nucleoplasmic ratio was increased, the nuclei were deeply stained, the nuclear schizophrenic phase was more, and the cell polarity was still present. Grade III: i.e. severe atypical hyperplasia and carcinoma in situ. The lesioned cells occupied almost or all of the epithelial layer, with abnormally enlarged nuclei, significantly increased nucleoplasmic ratio, deeper staining, more nuclear schizophrenic images, crowded cells, disorganized arrangement and no polarity.