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2020, Volume 36, Number 3, Page(s) 205-210     
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DOI: 10.5146/tjpath.2020.01494
Efficiency of Cytology Samples for PD-L1 Evaluation and Comparison with Tissue Samples
İbrahim KULAÇ1, Aslı AYDIN2, Pınar BULUTAY1, Pınar FIRAT1
1Department of Pathology, Koç University School of Medicine, İSTANBUL, TURKEY
2Department of Medical Student, Koç University School of Medicine, İSTANBUL, TURKEY
Keywords: PD-L1, Cytology, Cell blocks

Objective: Lung cancer is the leading cause of cancer-related death. PD-L1 blockers have become a first-line option for advanced non-small cell lung cancer (NSCLC) patients. Guidelines require the assessment of PD-L1 expression by immunohistochemistry. Although tissue samples are widely used, cytologic samples could be an alternative. In this study, we compared cytologic samples with tissue samples for PD-L1 evaluation in NSCLC cases.

Material and Method: Koç University Hospital, Department of Pathology Laboratory Information System was scanned for all PD-L1 tests performed on NSCLC cases, either on tissue samples or cell blocks. The type of the biopsy/aspiration procedure, the tumor type, patient demographics, and the percentage of PD-L1 positive tumor cells were recorded. A total of 73 tissue samples and 49 cell blocks were found to be eligible for the study.

Results: The PD-L1 positivity score was at least 1% in 44 of 73 samples of the tissue group and 19 of 49 samples of the cell block group. Tissue samples showed significantly higher positivity compared to the cell blocks (p=0.020). Comparing the frequency of cases with ≥50% positivity showed no statistically significant difference. A comparison of PD-L1 positivity rates of only the small biopsies and cell blocks also showed no significant difference.

Conclusion: Although they harbor a limited number of tumor cells, cell blocks prepared from cytologic samples are good alternatives for PD-L1 testing. However, large resections should be used for PD-L1 evaluation whenever possible since even 1% positivity may affect the treatment decision.

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