High MTHFD2 was associated with hormone receptor (ER, PgR) negative, HER2 positive breast cancer as well as with several other characteristics of poor clinical outcome such as p53 mutation, high grade tumors, lymph node (LN) positivity, increased risk of cancer death, basal subtype, increased proliferation measured by Ki67 and PCNA positivity (Fig. 3B). This evidence concerns the gene MKI67 and breast cancer.