As shown in Table 2 the expression of HDAC1 was positively correlated with the poor differentiation (P < 0.001), older age (P = 0.004) clinical stage (P = 0.007) and lymph node metastasis (P = 0.001), but was not related to the tumor size (P = 0.472) in the breast cancer tissues. The gene discussed is HDAC1; the disease is breast cancer.