ESR1 and neoplasm: Differentiated tumor cells were significantly more common in ER+ (93.1% ± 11.8 versus 50.5% ± 37.6 in ER-), Luminal A (97.9% ± 2.4 versus 48.7% ± 38.0 in TNBC), and BL1 TNBC (79.2% ± 16.2 versus 17.3% ± 23.7 in BL2; p < 0.05).