ESR1 and neoplasm: Representative staining results for ER and CAXII expression are shown from co-staining corresponding to the two most frequently observed phenotypes, ER+CAXII+ (71 tumors) and ER−CAXII− (37 tumors), and the two rarer phenotypes ER−CAXII+ (2 tumors, both HER2+) and ER+CAXII− (1 tumor) (Figure 7B).