ESR1 and neoplasm: Compared to IDC, ILC showed a larger tumor size (≥T2, 59.8% vs. 38.8%, P = 0.001), a lower histologic grade (HG 1/2, 90.4% vs. 64.4%, P < 0.001), more frequent estrogen receptor positive (90.4% vs. 64.4%, P < 0.001), progesterone receptor positive (71.1% vs. 50.1%, P < 0.001) and HER2 negative (97.5% vs. 74.6%, P < 0.001) status, and lower Ki-67 expression (10.3% ± 10.6% vs. 20.6% ± 19.8%, P < 0.001), as well as being more likely to be of the luminal A subtype (91.4% vs. 51.2%, P < 0.001).