Intraepithelial neoplasia, also known as intraepithelial neoplasia (IN), is a diagnostic term commonly used in clinical pathology diagnosis and covers atypical hyperplasia or heterogeneous proliferative lesions of epithelial tissues in several organs, including the cervix, prostate, endometrium, and esophagus and gastrointestinal organs of the digestive system. IN has obvious changes in cell morphology and cell arrangement compared with normal tissues, and there are also genetic clonal changes in its genetics, and its biological behavior is aggressive. The grade 2 method classifies intraepithelial neoplasia into low grade and high grade, where low grade corresponds to mild to moderate atypical hyperplasia and high grade corresponds to severe atypical hyperplasia or heterogeneous hyperplasia or carcinoma in situ. grade 2 method is more widely used in prostate gastrointestinal intraepithelial neoplasia. grade 3 method classifies intraepithelial neoplasia into low grade and high grade. The grade 3 method classifies intraepithelial tumors into grade 1, grade 2, and grade 3. grade 1 corresponds to mild atypical hyperplasia, grade 2 corresponds to moderate atypical hyperplasia, and grade 3 corresponds to severe atypical hyperplasia or heterogeneous hyperplasia or carcinoma in situ. grade 3 method has been widely used in the diagnosis of cervical epithelial lesions.