While estrogen negatively regulates TGF-β signaling to promote growth in ER positive breast cancers[21], the highly aggressive phenotypically homogeneous triple negative breast cancers (TNBC), lacking estrogen/progesterone receptors (ER/PR) and HER2, depend on TGF-β for growth and metastasis. The gene discussed is ERBB2; the disease is triple-negative breast carcinoma.