Fig. 1

ERα protein (a–c) and ESR1 mRNA (d) expression in oropharyngeal squamous cell carcinoma. Weak to moderate ERα expression < 10% of tumor cells (a ×400 magnification). Weak to moderate ERα expression in tumor cells diffusely (10–90%) (b ×400 magnification). Strong ERα expression in tumor cells diffusely (≥ 75%) (c ×400 magnification). ESR1 mRNA expression visualized by brown dotted (arrow) in tumor compartment (d ×600 magnification)