Atypical hyperplasia of the breast, also known as atypical hyperplasia and heterogeneous hyperplasia, is an abnormal proliferation of epithelial cells, which is characterized by an increase in the number of proliferating cells, varying sizes and morphology, and large and dense stained nuclei. The nucleoplasm ratio increases, and nuclear division may increase, but it is still mostly a normal nuclear division image, and the morphology shows a certain degree of heterogeneity, but it is not enough to diagnose as cancer. Atypical hyperplasia is the intermediate station from benign to malignant changes, and it is the key point from quantitative to qualitative changes. Therefore, atypical hyperplasia is called precancerous lesions, i.e. morphological changes of precancerous lesions, which mostly occur in the squamous epithelium of skin or mucosal surface, but also in the glandular epithelium. In this case, women should not be nervous, the prognosis is still very good.