Endometrial hyperplasia is of great clinical importance as a precursor to endometrial adenocarcinoma. It is also clinically important to clearly distinguish between endometrial hyperplasia, precancerous lesions and malignant neoplasms. Confusion can lead to under- or over-treatment because we need to treat the disease accordingly. Each type of precancerous lesion has a different clinical management, so we need a pathologic description that reflects the diagnostic criteria and clearly differentiates the clinicopathologic types of the different lesions. The “endometrial intraepithelial neoplasia” diagnosis and treatment system was born out of this desire. The system incorporates the advantages of the previous pathological diagnosis, while some modifications have been made. The new system is still based on the 4-category pathological diagnosis model proposed by the World Health Organization in 1994 for non-malignant endometrial diseases (in this model, atypical hyperplasia is equated with precancerous lesions). It is unclear whether diagnostic curettage or endometrial aspiration is superior in the diagnosis of precancerous lesions and whether they are combined with carcinogenesis; however, direct hysteroscopic sampling is clearly the most sensitive means of extraction. We recommend that surgery should be the first choice for patients with endometrial intraepithelial neoplasia when clinical circumstances allow. This is because total hysterectomy not only provides a definitive assessment of the disease (whether it is combined with cancer), but also provides effective treatment of precancerous lesions. However, when patients do not tolerate surgery or require preservation of reproductive function, systemic or local progestin application is a common alternative to hand substitution therapy, but its certainty needs further confirmation. Conclusions and recommendations Sensitive and precise diagnosis of endometrial precancerous lesions may reduce the likelihood of their development into invasive cancer. Based on available data and expert opinion, the American College of Obstetricians and Gynecologists and the Society of Gynecologic Oncology have developed the following consensus: The current system of pathologic description of endometrial intraepithelial neoplasia appears to be superior to the WHO 94 version of pathologic description. Each type of precancerous lesion has a different clinical management, so we need a terminology that reflects the diagnostic criteria and clearly differentiates the different clinicopathologic types of lesions. For this purpose, the “endometrial intraepithelial neoplasia” diagnostic system was developed, which combines and modifies the previous pathological diagnostic criteria. The new pathological criteria are based on the 1994 WHO model of four pathological types of non-malignant endometrial diseases (in this model, atypical hyperplasia is equated with precancerous lesions). “Endometrial intraepithelial neoplasia” is a better professional descriptor (better than “endometrial atypical hyperplasia”). For histologic sampling, we recommend direct hysteroscopy (although not mandatory) to obtain as much (small and scattered) lesion tissue as possible and to reduce background (normal endometrial tissue) interference. This will give us a better chance to confirm the diagnosis of a true precancerous lesion and to clarify whether it is combined with endometrial cancer. When clinical circumstances allow, total hysterectomy provides a definitive assessment (for combined cancer) of patients with endometrial intraepithelial neoplasia; and effective treatment of precancerous lesions. Subtotal hysterectomy, uterine fractionation, and endometrial resection are not indicated for patients with endometrial intraepithelial neoplasia. Systemic or local progestin is a common alternative to hysterectomy, but its validity needs to be further confirmed; it is generally used only in patients who are intolerant to surgery or who require preservation of reproductive function. In patients with endometrial intraepithelial neoplasia who opt for hormonal therapy without surgery, subsequent supervised follow-up examinations should include a series of endometrial biopsies every 3-6 months. However, the exact frequency of follow-up examinations has not been determined.