For ET, tamoxifen (56.2%) was the most frequently used adjuvant endocrine agent, followed by aromatase inhibitor (AI) (29.4%), tamoxifen plus gonadotropin‐releasing hormone agonist (GnRHa) (8.5%), and AI plus GnRHa (5.9%). Here, CYP19A1 is linked to essential thrombocythemia.