KRT19 and breast cancer: Serum CK19-2G2 levels in breast cancer patients (Mean = 3.66 mU/ml, SE = 0.61 mU/ml) were significantly higher than those of the healthy group (Mean = 0.58 mU/ml, SE = 0.07 mU/ml) and the benign group (Mean = 1.01 mU/ml, SE = 0.17 mU/ml).