AQP3 and neoplasm: To first establish the distribution of AQP3, AQP7 and AQP9 in mammary epithelium (experimental setup in Figure 1), we investigated acini in lobules and extralobular ducts in benign breast structures adjacent to tumor tissue in the immunohistochemical stainings of serial sections with antibodies against AQP3, AQP7 and AQP9, as well as the marker for myoepithelial cells (SMMS-1).