To assess for potential gain-of-function alterations affecting ESR1, we surveyed the Memorial Sloan Kettering (MSK) clinical sequencing breast cancer cohort, identifying 649 mutations in the LBD out of 8,302 samples analyzed (Figure 1A and Supplemental Table 1; supplemental material available online with this article; https://doi.org/10.1172/JCI163242DS1). The gene discussed is ESR1; the disease is breast cancer.