ESR1 and neoplasm: We first profiled treatment-naïve tumors of varying hormone receptor status, including “luminal” (ER+/PR+/HER2−), HER2+ (ER+/−/PR−/HER2+) and triple-negative (TN, ER−/PR−/HER2−) tumors, using immunofluorescent imaging and image cytometry and examining multiple tumor regions if possible (Fig. 1a, Supplementary Data 1).