PDCD1 and esophageal squamous cell carcinoma: In a separate study,13 PD1 and PD-L1 expression were assessed previously in tumor biospecimens from 349 patients with esophageal squamous cell carcinoma, and PD-L1 expression levels were found to correlate significantly with favorable outcome, whereas PD1 expression within the TME did not show any significant associations with clinicopathologic parameters.13