The Reproducibility of the Immunohistochemical PD-L1 Testing in Non-Small-Cell Lung Cancer: A Multicentric Italian Experience
Figure 1
(a) Case 1 (strong expressor); diversity in PD-L1 intensity using the two gold-standard methods; by SP263 clone, the positivity was easily evaluated at 4x; by 22C3, pathologists needed to apply a greater magnitude to confirm the reactivity in more than 50% of tumor cells. (b) Technical error. The core was not correctly evaluated due to detachment of the TMA section (case n.10). (c) Technical error. In the picture different levels of the same TMA-sampled core (n.18) hosted heterogeneous PD-L1 expressions. (d) Technical error. Case n.2 evaluated as intermediate expressor using protocol n.6. The board reviewers enhanced a false positive signal in the apex of tumor cells that was not present in the same tissue core whenever stained by other protocols. A similar technical artifact was observed also in case 3 from the same protocol.