Atypical hyperplasia is a pathological term that can occur on the covered epithelium of the surface of the skin or mucosa, or on the epithelium of glands. The atypical hyperplasia occurs mainly due to the chronic inflammatory stimulation of the epithelium, and although it is manifested by a variety of proliferating cell morphologies, most of them show normal nuclear division. Although the cell arrangement is disturbed and the polarity disappears, pathological nuclear division is not seen. Therefore, atypical hyperplasia is different from cancerous hyperplasia, which is a precancerous lesion.