ESR1 and head and neck squamous cell carcinoma: To achieve this goal, tumors of the oral cavity, larynx, and pharynx from The Cancer Genome Atlas Head and Neck Squamous Cell Carcinoma (TCGA-HNSC) cohort (n = 500) were ranked based on their ESR1 transcript levels and classified into ESR1-High (top quartile), ESR1-Low (bottom quartile), and ESR1-Moderate (all others) (Supplementary Figure S1A).