NDRG1 and metastatic malignant neoplasm: Second, in two independent datasets, NDRG1 expression is significantly higher in BrMs than in primary BCs, both in a paired analysis of 45 primary‐metastatic cancer pairs (p = 0.0347; paired Student t test) (Figure 5E) and in an unpaired analysis of 90 samples (p = 0.0497; Mann–Whitney U test) (Figure 5F).