TOP2A and breast cancer: Since the cells lining the terminal duct lobular units (TDLUs) are thought to be the precursor cells of breast cancer [12], in this cross-platform (microarray to IHC) validation analysis we focused primarily on the immunohistochemical expression of TOP2A, MCM2, and BUB1B in the histologically normal TDLUs, although we believe that these proteins may also be useful in the molecular stratification of benign breast disease and premalignant breast lesions such as atypical ductal hyperplasia (ADH).