ESR1 and neoplasm: To delineate the impact of unique tumor microenvironments from patients on standardized cancer cell lines, 110 patient-derived scaffolds (PDSs) were generated from biobanked primary breast tumors with available clinical follow-up data, including 89 ERα-positive, 19 ERα-negative tumors and 2 ERα status unknown (detailed patient characteristics in Supplementary Table S1).