<b>Methods:</b> Immunohistochemical expression of PD-L1 on tumour cells (TC) and tumour-infiltrating immune cells (TIC), and of PD-1 (programmed death receptor 1) on TIC was assessed using tissue microarrays with primary tumours and a subset of paired lymph node metastases from a consecutive, retrospective cohort of 174 patients with chemoradiotherapy-naïve EG adenocarcinoma.
PD-L1 expression was associated with high proliferative activity and the EMT phenotype in adenocarcinoma but not in squamous cell carcinoma of the lung.
PD-L1 expression was more frequently observed in the elderly (TCs P = 0.002), in males (TCs P = 0.029; TIICs P = 0.043), in patients with poorly differentiated adenocarcinoma with solid-type histological features (TCs P < 0.001; TIICs P < 0.001), in patients with MMR deficiency (TCs P < 0.001; TIICs P < 0.001), and in patients with EBV positivity (TCs P = 0.001; TIICs P = 0.050).
PD-L1 immunopositivity in TC or IC did not correlate with age, sex, stage or mutation status however sarcomatoid carcinoma and solid predominant adenocarcinomas showed higher positivity rates.
PD-L1 mRNA gene expression in lung cancers was higher than in most other tumor and normal tissue types and was significantly higher in lung SCC than adenocarcinoma (p < 0.001).
PD-L1 expression was thus compared by immunohistochemistry (IHC) versus RNA in situ hybridization (ISH) in 112 lung cancers by tissue microarray: 51 adenocarcinoma, 42 squamous cell carcinoma, 9 adenosquamous carcinoma, 5 carcinoid, 3 undifferentiated large cell carcinoma, 1 large cell neuroendocrine carcinoma, and 1 small cell carcinoma.
PD-L1 was highly expressed in 60% of all patients with AC, and the expression level was significantly correlated with <sup>18</sup>F-FDG uptake, glucose metabolism and hypoxia.
PD-L1 expression was adversely associated with epidermal growth factor receptor mutation status (P < .001) and was significantly associated with invasive adenocarcinomas rather than preinvasive lesions and minimally invasive adenocarcinomas (P < .001).
Programmed Death Ligand 1(PD-L1) testing is recommended for patients with Non-Small Cell Lung Cancer (NSCLC) at stage IIIB and IV, adenocarcinoma and squamous cell carcinoma.
PD-L1 expression in tumor cells was only seen in 3% (1/34) of ductal and 5% (2/42) of acinar adenocarcinomas (p = 1.0), while PD-L1 expression in tumor-infiltrating immune cells was seen in 29% (10/34) of ductal and 14% (6/42) of acinar adenocarcinomas (p = 0.16). dMMR, as defined by loss of one or more of the MMR proteins, was identified in 5% (4/73) of cases, including 1 ductal and 3 acinar adenocarcinomas.
A 73-year-old women known for myositis, Crohn's disease, and hypothyroidism and diagnosed with PD-L1 positive stage IV pulmonary adenocarcinoma is treated with Pembrolizumab.
A higher prevalence of PD-L1-positive cases was observed among esophageal specimens compared with gastric ones (p = 0.0003), in high-grade and adenocarcinoma samples in comparison with low-grade dysplasia (p < 0.0001), and in lesions with mismatch repair deficiency (p = 0.028).
A predominant adenocarcinoma epithelial component in PPC might be associated with better survival outcomes and high PD-L1 expression might be frequent in PPC.
A smaller population of tumors showed isolated PD-L1 (25% overall; 16% of adenocarcinomas, 44% of adenosquamous carcinomas, and 33% of squamous cell carcinomas) or IDO-1 expression (15% overall; 14% of adenocarcinomas, 11% of adenosquamous carcinomas, and 17% of squamous cell carcinomas).