ESR1 and breast cancer: To define the spatial pattern of FGF2 expression in relation to the immune cell infiltrates, we performed a multiplex IHC staining with a panel of four general immune cell markers (CD68, CD20, CD3, CD45, and pan cytokeratin) for 11 ER+ primary breast cancer samples selected from the previously stained samples (Fig. 5B–F, Supplementary Fig. 12).