Thymic epithelial tumors (TETs) are uncommon neoplasms of the mediastinum. The gold standard treatment is complete surgical resection which can be followed by radio/chemotherapy in selected cases. Targeted tyrosine kinase inhibition can be considered in only a limited number of aggressive or metastatic tumors as EGFR, BRAF, or c-kit mutations are rare. However, previous studies have demonstrated the efficacy of immune checkpoint inhibitors in epithelial neoplasias, such as in programmed cell death ligand 1 (PD-L1) expressing nonsmall cell lung carcinoma. Because of their rare occurrence the data on PD-L1 distribution in thymic neoplasias are limited. PD-L1 and PD-1 expression in tumor cells and tumor infiltrating immune cells was determined in TETs according to criteria published for lung carcinomas. Comparison with major clinical, pathologic, and biological features was also done. In total, 36 TETs (29 thymomas and 7 thymic carcinomas) were analyzed. PD-L1 immunohistochemical staining (Ventana PD-L1 clone SP142) was performed in all cases. The percentage of the positive tumor cells (TC value), the percentage of tumor area occupied by positive immune cells (IC value) was evaluated. Evaluation of PD-L1 expression in tumor cells showed a good reproducibility (κ-value: 0.840; Spearman r=0.966; P<0.0001). About 69% of thymomas (20/29) and 43% of thymic carcinomas (3/7) showed high positivity rate (TC≥50% or IC ≥10%), which may indicate therapeutic advantage similar to nonsmall cell lung cancers defined by the same conditions. PD-L1 expression is common in different epithelial tumors of the thymus, which suggests the potential effectiveness of drugs targeting the PD-1/PD-L1 interactions in these neoplasms.

中文翻译：

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程序性死亡配体 1 (PD-L1) 在胸腺上皮肿瘤中的表达

胸腺上皮肿瘤 (TET) 是罕见的纵隔肿瘤。金标准治疗是完全手术切除，在选定的病例中可以随后进行放疗/化疗。由于 EGFR、BRAF 或 c-kit 突变很少见，因此只能在有限数量的侵袭性或转移性肿瘤中考虑靶向酪氨酸激酶抑制。然而，之前的研究已经证明了免疫检查点抑制剂在上皮瘤形成中的功效，例如在表达程序性细胞死亡配体 1 (PD-L1) 的非小细胞肺癌中。由于它们很少发生，关于 PD-L1 在胸腺瘤中分布的数据是有限的。根据公布的肺癌标准，在 TET 中测定肿瘤细胞和肿瘤浸润免疫细胞中 PD-L1 和 PD-1 的表达。与主要临床、病理、生物特征也做了。总共分析了 36 个 TET（29 个胸腺瘤和 7 个胸腺癌）。所有病例均进行 PD-L1 免疫组织化学染色（Ventana PD-L1 克隆 SP142）。评估阳性肿瘤细胞的百分比（TC值），阳性免疫细胞所占肿瘤面积的百分比（IC值）。对肿瘤细胞中 PD-L1 表达的评估显示出良好的重现性（κ 值：0.840；Spearman r=0.966；P<0.0001）。大约 69% 的胸腺瘤 (20/29) 和 43% 的胸腺癌 (3/7) 显示出高阳性率（TC≥50% 或 IC ≥10%），这可能表明与非小细胞肺癌定义的非小细胞肺癌相似的治疗优势相同的条件。PD-L1 表达在胸腺不同的上皮肿瘤中很常见，