ESR1 and breast carcinoma: Figure 5 shows a case with ER-positive breast cancer on the upper outer quadrant of the left breast. PET images showed high homogeneous 16α-[18F]FES accumulation, and immunohistochemical findings of this case are high expression of ER. The other case with ER-negative breast cancer on the right axillary lymph node (Figure 6) showed no uptake on PET images, and immunohistochemical findings of this case are no expression of ER.