NETs are present in metastatic lesions of breast cancers such as liver, lungs, bones and brain, liver metastases having the most abundant infiltration (IHC: MPO and H3Cit stainings). Serum NETs level (detection of MPO/DNA complex) are significantly higher in patients with liver metastases. High levels of MPO/DNA was an independent variable associated with metastasis to the liver. The gene discussed is MPO; the disease is breast cancer.