Naso JR, Wang G, Pender A, et al. - A total of 166 non-small cell lung carcinoma resection specimens clinically tested for PD-L1 via the 22C3 pharmDx assay were recruited by the researchers in order to ascertain whether intratumoral PD-L1 variation was correlated with variations in local histotype, to recognize histotypes related to a tendency for higher or lower PD-L1 scores, and to determine the frequency of clinically important discordance in PD-L1 levels between intratumoral histotype areas. Intratumoral heterogeneity in PD-L1 was correlated with the difference in histotype. Over-representation of solid areas may enhance the PD-L1 score assigned to a tumor, whereas over-representing lepidic areas may reduce the PD-L1 score. Assessment of how histotype representation influences the predictive value of PD-L1 testing is guaranteed.