Onkológia 6/2018
Immunohistochemical expression of PD-L1 in biopsy specimen: how and why to examine?
The article describes, from the pathologist´s point of view, a summary of the data on examination and evaluation of the immunohistochemical expression of PD-L1 protein, which recently became to be used as an accepted predictive biomarker for the anti-PD-1/anti-PD-L1 immunotherapy of patients with different malignancies. Further follows an overview of the CE-IVD diagnostic imunohistochemical assays and the immunostainers required for the tests, as well as comment on limits of the application of other laboratory developed assays. The author explains the significance of the PD-L1 expression on tumor versus immune cells, the evaluation of the expression using tissue proportion score, as well as new scoring systems developed recently for assays with 22C3 – the combined positive and melanoma score. Finally, the article in agreement with the internationally accepted regulations comments the appropriateness of the certified methods of the PD-L1 testing for the real clinical practice and the correct interpretation of the results for the oncologist respecting the individual cut-off positivity values.
Keywords: PD-1 receptor, PD-L1 ligand, immunohistochemical expression, predictive tests, tissue proportion score, combined positive score, melanoma score
