ESR1 and breast neoplasm: Breast tumors with positive ER have a lower proliferation rate, while tumors with negative ER, a high histological grade, and HER2 positive status have a higher proliferation rate and have areas of necrosis and fibrosis that can be visualized on dynamic contrast-enhanced MRI (DCE MRI) and contrast-enhanced ultrasound (CEUS) as an inhomogeneous appearance because of perfusion defects or even rim enhancement in cases with central necrosis [15].