Cell-blocks are suitable material for programmed cell death ligand-1 immunohistochemistry: Comparison of cell-blocks and matched surgical resection specimens in lung cancer

Abstract

Objective: Programmed cell death ligand-1 (PD-L1) has emerged as a predictive biomarker in lung cancer. PD-L1 immunohistochemistry (IHC) assay predicts the response to immunotherapy, but cytology specimens are often the only samples available in a considerable proportion of advanced lung cancer patients. We delineate practical feasibility and efficacy of cytology cell-block (CB) specimens for PD-L1 expression and concordance between cytology CBs and surgical resection specimens.

Methods: In total, 58 eligible patients with primary lung cancer who received computed tomography-guided percutaneous needle aspiration and surgery were included. PD-L1 IHC (clone SP263) was performed on CBs prepared from residual liquid-based cytology material and matched surgical resection specimens. PD-L1 positive tumour cell proportion was categorised in four score groups: (a) <1%; (b) ≤1% to <10%; (c) ≤10% to <50%, (d) ≥50%.

Results: Comparison of PD-L1 expression in cytology CBs and matched surgical resection specimens showed a high concordance (κ value 0.65). According to the therapeutic guideline of immunotherapeutic agents, a positive percent agreement was 94.34%, and a negative percent agreement was 100% at a cut-off value for positivity of 1% PD-L1 expression. There was a significant difference observed with regard to rates of PD-L1 positivity when comparing smoking history (P = 0.02), age (P = 0.04) and pathological TNM stage (P = 0.04).

Conclusions: The results show that cytology CBs evaluated for PD-L1 IHC assay have high concordance with matched surgical resection specimens and can be used for assessing PD-L1 expression. Also, we propose that CBs are suitable materials for evaluating PD-L1 expression while simultaneously performing both diagnostic and molecular tests.

Keywords: cell-blocks; cytology; immune checkpoint therapy; lung cancer; matched surgical resection specimens; programmed cell death ligand-1.

Conflict of interest statement

The authors have no conflicts of interest to report.

© 2019 The Authors. Cytopathology Published by John Wiley & Sons Ltd.

Figures

Figure 1

Programmed cell death ligand‐1 (PD‐L1) immunohistochemical staining on cytology cell blocks and matched histology slides (A and B) Case 1. The cytology cell block (A) and matched histology (B) slides showed no PD‐L1 positive tumour cells (×100; C and D) Case 2. Both slides showed more than 1%, but less than 10% PD‐L1 positivity in adenocarcinoma. (×100; E and F) Case 3. Squamous cell carcinoma showed more than 1%, but less than 10% PD‐L1 positivity in cytology and histology slides (×100; G and H) Case 4. High PD‐L1 expression, more than 50%, was observed in G and H (G: ×100, H: ×40)

Figure 2

The only case of substantial PD‐L1 discrepancy (A) The cytology CB specimen showed less than 1% PD‐L1 positivity. (x40) (B) The matched surgical resection specimen from the same patient showed heterogeneous PD‐L1 positivity. The final score was 2. (x10) (C) The high magnification view of dashed line circle in Figure 2(B) showed less than 1% PD‐L1 positivity, the same PD‐L1 result of the cytology CB specimen. (x100) (D) The high magnification view of solid line circle in Figure 2(B) showed near 80% PD‐L1 positivity, the discordant PD‐L1 result of the cytology CB specimen. (x100)