Abstract: ObjectiveTo study the expression and significance of P33/ING1 and HIF-1α in invasive ductal carcinoma of breast(IDC). MethodsImmunohistochemical SP method was performed to detect the expression of P33/ING1 and HIF-1α in 68 cases of IDC and 20 cases of breast fibroadenoma and the relationship between the expression and clinical-pathological characteristics was analyzed. ResultsThe positive expression rates of P33/ING1 protein in IDC was significant lower than that in breast fibroadenoma (60.29% vs. 95%；P<0.01);and negatively correlated with tumor size, axillary lymph node metastasis and histologic grade(P<0.05).The positive expression rates of HIF-1α protein in IDC was significant higher than that in breast fibroadenoma (52.94% vs. 10%; P<0.01) and positively correlated with axillary lymph node metastasis and histologic grade(P<0.05). There was a negatively correlation between P33/ING1 and HIF-1α in IDC (r=-0.283；P<0.05). ConclusionThere were low-expression of P33/ING1 and over-expression of HIF-1α in IDC. P33/ING1 and HIF-1α proteins were significantly correlated with the clinicopathological characteristics in IDC. Combined detection of P33/ING1 and HIF-1α might calculate the biological behaviors of IDC.