We performed immunohistochemistry analysis in 194 cases of invasive ductal carcinoma (IDC), and found that high cytoplasmic expression of AQP1 was positively associated with metastasis or recurrence (P = 0.009), lymph node metastasis (P = 0.038), tumor size (P = 0.003), and pTNM stage (P = 0.003) (Supplementary Fig. 1a, b and Supplementary Table S3). The gene discussed is AQP1; the disease is metastatic malignant neoplasm in the lymph nodes.