Considering the proof of the key role of mutation of some tumor suppressor genes such as p53 in the incidence of some cancers as well as changes in the incidence of the cell cycle regulator protein and cellular proliferation marker Ki-67 as well as the expression of HER-2/neu and CD44 genes in many cancers, the relationship between their immunohistochemistry, clinical, and pathological indicators of tumors can be determined. The gene discussed is MKI67; the disease is cancer.