A separate analysis of 30 breast cancer cases revealed that CSE was: (1) higher in breast cancer than adjacent benign breast tissue, (2) increased in stage III cancers compared to stage II, (3) highest in metastatic disease, and (4) higher in ER, PR, and HER2/Neu immunonegative tumors (triple negative/basaloid breast cancer). Here, ERBB2 is linked to cancer.