41.9% (143/341) of IDC, 28.9% (13/45) of DCIS and 15.2% (5/33) of benign breast lesions showed high cytoplasmic expression of AQP1, indicating that cytoplasmic AQP1 probably be involved in breast cancer progression (Table 1). This evidence concerns the gene AQP1 and ductal breast carcinoma in situ.