The characteristics of tumor cells are mainly manifested in spatial arrangement, cell size, nuclear traits and cytoplasm, as follows: First, spatial arrangement: the differences between tumor tissues in spatial arrangement and their normal tissues of origin are manifested in the changes of tumor cells in terms of arrangement, hierarchy and polarity. For example, in esophageal squamous cell carcinoma, the arrangement of squamous epithelium is significantly disturbed, and in endometrial adenocarcinoma, the normal endometrial mesenchyme between the glands disappears, etc. Second, cell size: the size and morphology of tumor cells are inconsistent and appear polymorphic, such as tumor giant cells. Third, nuclear traits: the nuclei of tumor cells appear abnormal, with different sizes, disproportionate nuclear plasma, deep nuclear staining, coarse chromatin, and increased nuclear schizophrenia. Fourth, cytoplasm: the cytoplasm of tumor cells is altered, often with basophils producing abnormal secretions or metabolites, which has certain significance to the diagnosis and treatment of tumor.