Although the activation of de novo serine biosynthesis in cancer was described nearly 30 years ago, recent identification of PHGDH amplification or overexpression in breast cancer and melanoma has reignited interest in the role of this pathway in tumorigenesis.[36] Cancer cells with high PHGDH expression exhibit increased levels of de novo serine biosynthesis and, unsurprisingly, have a reduced dependency on exogenous L‐serine for growth. This evidence concerns the gene PHGDH and breast cancer.