Malignant pleural effusion cell blocks are reliable resources for PD-L1 analysis in advanced lung adenocarcinomas: a concordance study with matched histologic samples.

Swati Mahajan, Aruna Nambirajan, Ishan Gupta, Nalini Gupta, Parikshaa Gupta, Deepali Jain

Journal of the American Society of Cytopathology 2022 Sep-Oct

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In lung cancer patients presenting with malignant pleural effusion (MPE), cytology might represent the only source of tumor tissue for diagnosis and predictive biomarker testing. Programmed death ligand 1 (PD-L1) expression in tumor cells is a predictive biomarker for immunotherapy in non-small cell lung carcinomas and is tested using immunohistochemistry. However, knowledge of the validity of PD-L1 testing on MPE samples is limited. We evaluated the feasibility of immunocytochemistry (ICC) for PD-L1 in MPE cell blocks (CBs) and assessed the concordance in expression with patient-matched histologic samples. ICC for PD-L1 was performed on formalin-fixed paraffin-embedded CBs of MPE and patient-matched histologic samples, if available, using the automated Ventana PD-L1 SP263 assay. The tumor proportion score (TPS), based on partial or complete membranous tumor cell staining, was categorized as negative (<1%), low (≥1% to <50%), and high (≥50%). In CBs with any degree of PD-L1 expression, ICC for CD163 highlighting macrophages was performed to exclude nonspecific PD-L1 expression in macrophages. The CB PD-L1 TPS was compared with the TPS obtained from the patient-matched histologic samples. Of 43 MPE CBs available, 25 were positive for PD-L1 (25 of 42; 59%), and 1 sample was inadequate. Of the 11 patient-matched histologic samples tested, the PD-L1 TPS categories were concordant for 10 of the 11 (91% concordance) cases. PD-L1 expression in MPE CBs showed good concordance with expression in histologic samples and is feasible as a source for PD-L1 testing. The concurrent use of CD163 immunostains will aid in the manual assessment of PD-L1 TPS. Copyright © 2022 American Society of Cytopathology. Published by Elsevier Inc. All rights reserved.

Citation

Swati Mahajan, Aruna Nambirajan, Ishan Gupta, Nalini Gupta, Parikshaa Gupta, Deepali Jain. Malignant pleural effusion cell blocks are reliable resources for PD-L1 analysis in advanced lung adenocarcinomas: a concordance study with matched histologic samples. Journal of the American Society of Cytopathology. 2022 Sep-Oct;11(5):253-263