Interobserver agreement in programmed cell death-ligand 1 immunohistochemistry scoring in nonsmall cell lung carcinoma cytologic specimens

BACKGROUND

The evaluation of PD-L1 expression in nonsmall cell lung carcinoma (NSCLC) is becoming increasingly important given the effectiveness of PD-L1 inhibitors. Although cytologic specimens have been shown to be compatible with surgical specimens to evaluate PD-L1 immunohistochemistry (IHC), evidence of the reproducibility of PD-L1 in cytologic specimens is lacking. The aim of this study is to evaluate interobserver agreement in PD-L1 IHC in cytologic specimens.

METHODS

PD-L1 IHC was performed on 86 NSCLC cytology specimens using Dako PD-L1 IHC 22C3 pharmDx. The digitally scanned whole slide images (WSI) were read by five pathologists. Each case was given a Tumor Proportion Score (TPS) and the results were compared between the observers. The interobserver concordance was assessed using 1% and 50% as cutoffs.

RESULTS

TPSs were highly correlated among observers (Spearman correlation coefficient, 0.86-0.94). Using greater than 1% as a cutoff, interobserver agreement measured by Fleiss Kappa was 0.74 for all pathologists and Cohen's Kappa coefficient ranged from 0.49 to 0.83, consistent with moderate to substantial agreement. With a cutoff of greater than 50%, Fleiss Kappa was 0.79 for all pathologists and the kappa values ranged from 0.63 to 0.90, consistent with substantial to almost perfect agreement. Several pitfalls were identified by reviewing discordant cases, including staining in macrophages, stromal cells, and intratumoral heterogeneity.

CONCLUSION

Our data suggest that TPS of PD-L1 IHC on cytology specimens is reproducible, with a better agreement when using 50% as the cutoff value. However, special attention is required when the TPS is near the 1% cutoff.

Congenital Salivary Gland Anlage Tumor: An Unusual Anterior Skull Base Mass in the Neonatal Period

Congenital salivary gland anlage tumor (SGAT) is a benign nasopharyngeal mass that presents with respiratory distress in infancy. Prior case reports have characterized SGAT as a lesion of the nasopharynx without intracranial extension. We report a unique case of SGAT extending through the anterior skull base and discuss the differential diagnosis and management of this unusual entity.