A new study in the Journal of Hematology & Oncology examines how often the immune checkpoint proteins PD-1 and PD-L1 are found in thymic epithelial tumors (TETs). These rare tumors develop in the front of the chest and include several types of thymomas and thymic carcinomas. The researchers aimed to understand expression patterns and whether testing could help guide diagnosis or treatment.
The study reviewed tumor samples from 70 patients with confirmed TETs. Pathologists classified the tumors by World Health Organization type. The team used immunohistochemistry (IHC) to detect PD-1 and PD-L1, scoring the results to measure how strongly they were expressed.
PD-1 was mostly seen in immune cells inside the tumors, especially in B2 and B3 thymomas. PD-L1, however, was present in the tumor cells themselves and was more common and stronger in thymic carcinomas. Over 80 percent of thymic carcinoma samples showed high PD-L1 expression. Higher PD-L1 levels were linked to more advanced disease stages.
The study did not find a clear link between PD-1 levels and survival, but patients with high PD-L1 sometimes had worse outcomes. The authors said more research is needed to confirm whether PD-L1 has prognostic value.
PD-L1 testing could be a useful addition when pathologists examine TETs, similar to its use in other cancers. The results suggest it may help classify tumors and possibly identify patients for immune checkpoint inhibitor therapy. However, the benefit of such drugs for TETs is not yet proven.
The study was small, from a single center, and retrospective. Differences in IHC methods between labs could also affect results. The authors recommend standardizing PD-L1 testing in TETs to make results more consistent.
Overall, this work adds to the evidence on immune markers in rare thoracic tumors and may help guide diagnostic practices in the future.
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