PD-L1 Expression in Cytological and Histological Lung Cancer Specimens

Abstract

Abstract Introduction/Objective Several studies have explored the feasibility of measuring PD-L1 in cell block cytology and indicated cytological materials could be a reliable source for PD-L1 evaluation in non-small cell lung carcinoma patients. A few studies have investigated the compatibility and performance of PD-L1 clone SP263 testing between cytology and histology specimens. The study was pursued to evaluate PD-L1 expression in cell blocks from EBUS- TBNA compared to that in biopsied tissues from patients with lung carcinoma in our institution to evaluate a feasibility of PD-L1 clone SP263 in cell blocks and histology samples. Methods/Case Report A total of 57 specimens cytologically diagnosed lung carcinoma using endobronchial ultrasound guided transbronchial needle aspiraton (EBUS-TBNA) from Jan 1st, 2020, to Dec 31st, 2021 were screened for enrollment. Among them, 24 patients diagnosed with lung carcinoma using EBUS-TBNA and matched transbronchial biopsy (TBB) specimens were reviewed for study. After careful selection, 13 paired formalin-fixed tissues from lung carcinoma patients, including cell blocks and matched histology samples, were included. PD-L1 expression was assessed using the SP263 assay, and the tumor proportion score (TPS) was evaluated. PD-L1 expression was finally divided into three categories according to the TPS: < 1% (negative), 1–49% (low expression) and ≥ 50% (high expression). Results (if a Case Study enter NA) Of the 13 matched pairs, 12 (92.3%) showed concordant PD-L1 expression. On cytology, 3 cases were positive (2 high expressors and 1 low- expressors) of which 2 were concordant and 1 discordant with matched histology specimens. Ten cytology samples were negative for PD-L1 expression, and they were concordant to histology samples. The correlation coefficient for TPS was 0.75 considered as having good value. Conclusion: With an overall concordance rate of 92.3% between cytology and histology specimen, this study demonstrates the feasibility of PD-L1 IHC with SP263 clone on limited quality and quantity of cytology samples from lung carcinoma in our institute. It is required for further evaluation with additional specimens to conclude that the usefulness of cytology cell blocks for PD-L1 expression analysis.