Turkish Journal of Pathology

Türk Patoloji Dergisi

Turkish Journal of Pathology

Turkish Journal of Pathology

2020, Vol 36, Num, 3     (Pages: 205-210)

Efficiency of Cytology Samples for PD-L1 Evaluation and Comparison with Tissue Samples

İbrahim KULAÇ 1, Aslı AYDIN 2, Pınar BULUTAY 1, Pınar FIRAT 1

1 Department of Pathology, Koç University School of Medicine, İSTANBUL, TURKEY
2 Department of Medical Student, Koç University School of Medicine, İSTANBUL, TURKEY

DOI: 10.5146/tjpath.2020.01494
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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.

Keywords : PD-L1, Cytology, Cell blocks