RRM2 and ductal breast carcinoma in situ: Among the 146 samples analyzed herein, CDK1, NUSAP1, CEP55, TOP2A, MELK, PBK, RRM2, and MAD2L1 were significantly correlated with the eigengene in the black module and were upregulated in DCIS compared with normal tissues; thus, they were defined as hub genes for breast cancer pathogenesis.