ESR1 and neoplasm: Since 2010, the guidelines for immunohistochemical analysis have defined negativity as less than 1% of tumor cells with positive ER or PR staining.3 However, during our study period, the cutoff for defining hormone receptor negativity was not uniform, and it remains unclear whether the cutoff included a range of 1% to 10% or more in some SEER registries.35 Therefore, it would be more appropriate to consider ER-negative and PR-negative status as less than 10% of positively stained cells when interpreting the results of this study.