In our study, we found that the frequency of single KRAS mutations was significantly higher in group 3, and the concordance of which with the paired neoplasia endometrial tissues was also elevated statistically in group 3, while no difference was found between the groups of different quantity of simple papillae, suggesting that the 2-tier classification emphasizing the complex papillae could reflect a distinctive KRAS characteristics of the complex PPE. The gene discussed is KRAS; the disease is neoplasm.