Adequate tumour cellularity is essential for accurate PD-L1 immunohistochemistry assessment on cytology cell-block specimens

The detection of PD-L1 expression on liquid-based cytology in pleural effusion of lung adenocarcinoma and its prognostic evaluation: Between paired liquid-based cytology and cell block samples

BACKGROUND

Programmed death-ligand 1 (PD-L1) expression levels measured by immunohistochemistry have been proven to predict the outcome of immunotherapy in lung adenocarcinoma (LUAD). However, data on PD-L1 expression on liquid-based cytology (LBC) in malignant pleural effusion (MPE) is scarce.

METHODS

This study cohort included 60 cases with MPE suffering from LUAD. PD-L1 SP263 assay was used for immunocytochemistry (ICC) on LBC and matched cell block (CB) to validate ICC protocols on LBC slides. Clinical outcomes were analyzed based on immunotherapy and PD-L1 tumor proportion scores (TPS) on LBC slides and CBs.

RESULTS

PD-L1 expression with TPS ≥1% was lower in LBCs than in CBs (33 of 60 [55.0%] vs. 35 of 60 [58.3%]; p = .687). Even with the TPS ≥50% threshold, PD-L1 expression was lower in LBCs (10 of 60 [16.7%] vs. 15 of 60 [25%]; p = .125). Epidermal growth factor receptor (EGFR) exon 20 mutation, tumor cell proportion, and pleural fluid neutrophil-to-lymphocyte ratio were related to PD-L1 expression on CBs (p = .013, p = 0.022, and p = .011), respectively. Patients with subsequent immune checkpoint inhibitor therapy remained a better prognostic in subgroups of PD-L1 positive expression on LBC slides (TPS ≥1%, p = .041).

CONCLUSIONS

LBC specimens had comparable performance to CBs in PD-L1 assessment and predicting treatment response to PD-L1-defined therapy.

Comparison of the specimen quality of endobronchial ultrasound-guided intranodal forceps biopsy using standard-sized forceps versus mini forceps for lung cancer: A prospective study

BACKGROUND AND OBJECTIVE

Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is a diagnostic procedure with adequate performance; however, its ability to provide specimens of sufficient quality and quantity for treatment decision-making in advanced-stage lung cancer may be limited, primarily due to blood contamination. The use of a 0.96-mm miniforceps biopsy (MFB) permits true histological sampling, but the resulting small specimens are unsuitable for the intended applications. Therefore, we introduced a 1.9-mm standard-sized forceps biopsy (SFB) and compared its utility to that of MFB.

METHODS

We prospectively enrolled patients from three institutions who presented with hilar/mediastinal lymphadenopathy and suspected advanced-stage lung cancer, or those who were already diagnosed but required additional tissue specimens for biomarker analysis. Each patient underwent MFB followed by SFB three or four times through the tract created by TBNA using a 22-gauge needle on the same lymph node (LN). Two pathologists assessed the quality and size of each specimen using a virtual slide system, and diagnostic performance was compared between the MFB and SFB groups.

RESULTS

Among the 60 enrolled patients, 70.0% were diagnosed with adenocarcinoma. The most frequently targeted sites were the lower paratracheal LNs, followed by the interlobar LNs. The diagnostic yields of TBNA, MFB and SFB were 91.7%, 93.3% and 96.7%, respectively. The sampling rate of high-quality specimens was significantly higher in the SFB group. Moreover, the mean specimen size for SFB was three times larger than for MFB.

CONCLUSION

SFB is useful for obtaining sufficient qualitative and quantitative specimens.

Accuracy of Cytologic vs Histologic Specimens for Assessment of Programmed Cell Death Ligand-1 Expression in Non-Small Cell Lung Cancer: A Systematic Review and Meta-Analysis

BACKGROUND

Programmed cell death ligand-1 (PD-L1) expression on tumor cells, evaluated by immunohistochemistry, guides the use of immunotherapy in advanced non-small cell lung cancer (NSCLC).

RESEARCH QUESTION

What is the sensitivity and specificity of PD-L1 testing performed in cytologic vs paired histologic specimens in patients with NSCLC?

STUDY DESIGN AND METHODS

The MEDLINE, Embase, Web of Science, and Cochrane Library databases were searched through June 1, 2021. The primary outcome was pooled sensitivity and specificity of PD-L1 testing performed on cytologic specimens compared with the reference standard of histologic specimens, analyzed at the PD-L1 expression cutoffs (tumor proportion score) ≥ 1% and ≥ 50%. Pooled sensitivity and specificity, and associated 95% CIs, were estimated using bivariate generalized linear mixed models.

RESULTS

Twenty-six articles were included, encompassing a total of 1,064 pairs of histology specimens and cytology cell blocks, and 267 pairs of histology specimens and direct smears. Among these, 946 paired specimens were acquired without interval treatment between the collection of histology and cytology samples. The pooled sensitivity and specificity of cytology specimens compared with paired histology specimens at the PD-L1 expression cutoff ≥ 1% were 0.84 (95% CI, 0.77-0.89) and 0.88 (95% CI, 0.82-0.93), respectively, whereas the pooled sensitivity and specificity at cutoff ≥ 50% were 0.78 (95% CI, 0.69-0.86) and 0.94 (95% CI, 0.91-0.96), respectively. When only paired specimens acquired without interval treatment were considered, the pooled sensitivity and specificity of cytology specimens at PD-L1 expression cutoff ≥ 1% were 0.84 (95% CI, 0.76-0.90) and 0.89 (95% CI, 0.82-0.94), respectively, whereas the pooled sensitivity and specificity at cutoff ≥ 50% were 0.80 (95% CI, 0.71-0.89) and 0.94 (95% CI, 0.91-0.96), respectively.

INTERPRETATION

Cytologic specimens provide an accurate assessment of PD-L1 expression in most patients with NSCLC, at both ≥ 1% and ≥ 50% cutoffs, when compared with histologic specimens.

TRIAL REGISTRATION

PROSPERO; No.: CRD42020153279; URL: https://www.crd.york.ac.uk/prospero/.

Adequacy of cytology and small biopsy samples obtained with rapid onsite evaluation (ROSE) for predictive biomarker testing in non-small cell lung cancer

Complete biomarker workup of non-small cell lung cancer (NSCLC) specimens is essential for appropriate and timely clinical management decisions. This can be challenging to achieve from small cytology and histology specimens, with increasing numbers of molecular and immunohistochemical biomarkers required. We conducted a 5 year retrospective audit of cases at our institution to assess the diagnostic and biomarker testing adequacy rates, particularly those specimens obtained with rapid onsite evaluation (ROSE), performed by a cytopathologist and a cytology scientist or pathology trainee, including all endobronchial ultrasound guided transbronchial needle aspirations (EBUS-TBNA), CT guided lung fine needle aspirations (FNA) and CT guided lung core biopsies. A total of 5,354 cases were identified, of which 92.2% had sufficient material for diagnosis. Of the 1506 cases identified with a recorded diagnosis of lung adenocarcinoma or NSCLC, not otherwise specified, 1001 (66.5%) had biomarker testing requested. Sufficient material was available in 89.5% of cases for a complete biomarker workup which included EGFR and KRAS mutational testing (all cases), ALK, ROS1 and PD-L1 immunohistochemistry (all cases), and ALK and ROS1 FISH (as required). For EGFR and KRAS mutational testing across both cytology and histology specimens, 99% of cases were sufficient. Of the samples in which a complete biomarker workup was unable to be performed, approximately half were only insufficient due to inadequate numbers of tumour cells for PD-L1 immunohistochemistry. Excluding PD-L1 IHC, 952 (95.1%) of samples obtained with ROSE were sufficient for the remainder of the testing requirements. Next generation sequencing using a 33 gene custom AmpliSeq panel was achieved in up to 72% of cases. In conclusion, small cytology and histology specimens obtained with ROSE are suitable for predictive biomarker testing in NSCLC, although attention needs to be paid to obtaining sufficient cells (>100) for PD-L1 immunohistochemistry.

Endobronchial ultrasound in diagnosing and staging of lung cancer by Acquire 22G TBNB versus regular 22G TBNA needles: A randomized clinical trial

OBJECTIVES

Endobronchial ultrasound guided transbronchial needle aspiration (EBUS-TBNA) has an important role in the diagnosis and staging of lung cancer. Evaluation of programmed death ligand 1 (PD-L1) expression and molecular profiling has become standard of care but cytological samples frequently contain insufficient tumor cells. The 22G Acquire needle with Franseen needle tip was developed to perform transbronchial needle biopsy (TBNB) with improved tissue specimens. This study evaluated if the 22G Acquire TBNB needle results in enhanced PD-L1 suitability rate compared to the regular Expect 22G TBNA needle.

METHODS

in this multi-center randomized clinical trial (Netherlands Trial Register NL7701), patients with suspected (N)SCLC and an indication for mediastinal/hilar staging or lung tumor diagnosis were recruited in five university and general hospitals in the Netherlands, Poland, Italy and Czech Republic. Patients were randomized (1:1) between the two needles. Two blinded reference pathologists evaluated the samples. The primary outcome was PD-L1 suitability rate in patients with a final diagnosis of lung cancer. In case no malignancy was diagnosed, the reference standard was surgical verification or 6 month follow-up.

RESULTS

154 patients were randomized (n = 76 Acquire TBNB; n = 78 Expect TBNA) of which 92.9% (n = 143) had a final malignant diagnosis. Suitability for PD-L1 analysis was 80.0% (n = 56/70; 95 %CI 0.68-0.94) with the Acquire needle and 76.7% (n = 56/73; 95 %CI 0.65-0.85) with the Expect needle (p = 0.633). Acquire TBNB needle specimens provided more frequent superior quality (65.3% (95 %CI 0.57-0.73) vs 49.4% (95 %CI 0.41-0.57, p = 0.005) and contained more tissue cores (72.0% (95 %CI 0.60-0.81) vs 41.0% (95 %CI 0.31-0.54, p < 0.01). There were no statistically significant differences in tissue adequacy, suitability for molecular analysis and sensitivity for malignancy and N2/N3 disease.

CONCLUSION

The 22G Acquire TBNB needle procured improved quality tissue specimens compared to the Expect TBNA needle but this did not result in an improved the suitability rate for PD-L1 analysis.

The Role of Checkpoint Inhibitor Expression Directly on Exfoliated Cells from Bladder Cancer: A Narrative Review

Bladder cancer (BCa) is a common type of cancer that affects the urinary bladder. The early detection and management of BCa is critical for successful treatment and patient outcomes. In recent years, researchers have been exploring the use of biomarkers as a non-invasive and effective tool for the detection and monitoring of BCa. One such biomarker is programmed death-ligand 1 (PD-L1), which is expressed on the surface of cancer cells and plays a crucial role in the evasion of the immune system. Studies have shown that the PD-L1 expression is higher in BCa tumors than in healthy bladder tissue. Additionally, PD-L1 expression might even be detected in urine samples in BCa patients, in addition to the examination of a histological sample. The technique is being standardized and optimized. We reported how BCa patients had higher urinary PD-L1 levels than controls by considering BCa tumors expressing PD-L1 in the tissue specimen. The expression of PD-L1 in urinary BCa cells might represent both a diagnostic and a prognostic tool, with the perspective that the PD-L1 expression of exfoliate urinary cells might reveal and anticipate eventual BCa recurrence or progression. Further prospective and longitudinal studies are needed to assess the expression of PD-L1 as a biomarker for the monitoring of BCa patients. The use of PD-L1 as a biomarker for the detection and monitoring of BCa has the potential to significantly improve patient outcomes by allowing for earlier detection and more effective management of the disease.

Comparing per-pass performance of 2 types of needles for EUS-guided fine-needle biopsy sampling of pancreatobiliary masses in a randomized trial

BACKGROUND AND AIMS

EUS-guided fine-needle biopsy sampling (EUS-FNB) has largely replaced FNA for tissue diagnosis of pancreatobiliary mass lesions. However, the optimal number of passes required for the diagnosis of malignancy is not clear. We aimed to compare the per-pass performance of 2 types of fine-needle biopsy (FNB) needles for the detection of malignancy.

METHODS

One hundred fourteen patients referred for EUS evaluation of solid pancreatobiliary mass lesions underwent randomization between biopsy sampling with a Franseen needle and a 3-prong tip needle with an asymmetric cutting surfaces. Four passes of EUS-FNB were taken from each mass lesion. Two pathologists blinded to needle type analyzed the specimens. The final diagnosis of malignancy was made based on FNB specimen pathology, surgery, or a follow-up of at least 6 months after EUS-FNB. The sensitivity of EUS-FNB to diagnose malignancy was compared between the 2 groups. The cumulative sensitivity of detection of malignancy by EUS-FNB was calculated after each pass in each arm. Other characteristics of the specimens including cellularity and blood contents were also compared between the 2 groups. In the primary analysis, lesions categorized as suspicious on EUS-FNB were considered nondiagnostic for malignancy.

RESULTS

Ninety-eight patients (86%) had a final diagnosis of malignancy, and 16 patients (14%) had benign disease. Four passes of EUS-FNB with the Franseen needle detected malignancy in 44 of 47 patients (sensitivity, 93.6%; 95% confidence interval [CI], 82.5-98.7) and with the 3-prong asymmetric-tip needle in 50 of 51 patients (sensitivity, 98%; 95% CI, 89.6-99.9; P = .35). Two passes of EUS-FNB detected malignancy with a sensitivity of 91.5% (95% CI, 79.6-97.6) with the Franseen needle and 90.2% (95% CI, 78.6-96.7) with the 3-prong asymmetric-tip needle. The cumulative sensitivities at pass 3 were 93.6% (95% CI, 82.5-98.6) and 96.1% (95% CI, 86.5-99.5), respectively. Samples collected with the Franseen needle had significantly higher cellularity than samples collected with the 3-prong asymmetric-tip needle (P < .01). However, no difference as found between the 2 types of needles in term of specimen bloodiness.

CONCLUSIONS

No significant differences were found in the diagnostic performance of the Franseen needle versus the 3-prong asymmetric-tip needle in patients with suspected pancreatobiliary cancer. However, the Franseen needle yielded higher cellularity of the specimen. Two passes of EUS-FNB are required to detect malignancy with at least 90% sensitivity with either type of needle. (Clinical trial registration number: NCT04975620.).

Proposed quality indicators and recommended standard reporting items in performance of EBUS bronchoscopy: An official World Association for Bronchology and Interventional Pulmonology Expert Panel consensus statement

BACKGROUND

Since their introduction, both linear and radial endobronchial ultrasound (EBUS) have become an integral component of the practice of Pulmonology and Thoracic Oncology. The quality of health care can be measured by comparing the performance of an individual or a health service with an ideal threshold or benchmark. The taskforce sought to evaluate quality indicators in EBUS bronchoscopy based on clinical relevance/importance and on the basis that observed significant variation in outcomes indicates potential for improvement in health care outcomes.

METHODS

A comprehensive literature review informed the composition of a comprehensive list of candidate quality indicators in EBUS. A multiple-round modified Delphi consensus process was subsequently performed with the aim of reaching consensus over a final list of quality indicators and performance targets for these indicators. Standard reporting items were developed, with a strong preference for items where evidence demonstrates a relationship with quality indicator outcomes.

RESULTS

Twelve quality Indicators are proposed, with performance targets supported by evidence from the literature. Standardized reporting items for both radial and linear EBUS are recommended, with evidence supporting their utility in assessing procedural outcomes presented.

CONCLUSION

This statement is intended to provide a framework for individual proceduralists to assess the quality of EBUS they provide their patients through the identification of clinically relevant, feasible quality measures. Emphasis is placed on outcome measures, with a preference for consistent terminology to allow communication and benchmarking between centres.

PD-L1 immunohistochemical testing: A review with reference to cytology specimens

BACKGROUND

Immunotherapy based on disruption of the PD-1/PD-L1 axis is standard of care for many high stage malignancies including melanomas, non-small cell carcinomas of the lung, triple negative breast carcinomas, and squamous cell carcinomas of the head and neck. Eligibility for immunotherapy requires immunohistochemical assessment of PD-L1 expression. Currently, many high stage malignancies are diagnosed by cytology and cytologic material is the only specimen available for ancillary testing. Formal guidelines do not currently exist defining the optimal specimen type, antibody to be used or the best scoring system for cytologic material. Significant information has been published for PD-L1 testing of pulmonary specimens but much less data exists for the reproducibility, accuracy and best practices for material obtained from other body sites and types of malignancy.

METHODS

We searched the PubMed data base for manuscripts relating to PD-L1 testing of cytologic specimens. The search period was between 2016 and 2022. The search terms used were PD-L1, cytology, FNA, immunotherapy, immunohistochemistry, immunocytochemistry, cytology-histology correlation. Cross referencing techniques were used to screen for the most relevant manuscripts. The abstracts of these were then reviewed for final data collection and analysis.

RESULTS

A total of 86 studies were identified conforming to study relevancy. These were reviewed in their entirety by two authors (LJL, TZ) for extraction of data. The majority of studies involved pulmonary specimens (79) with three relating to PD-L1 testing of head and neck cytologic specimens and one each for PD-L1 testing of cytology specimens from melanomas, pancreas, pleural fluids, and triple negative breast carcinomas. While smears could be used, most studies found cell blocks optimal for testing.

SUMMARY

Currently, four drugs are approved for immunotherapy based on PD-L1 status. These drugs require specific antibody clones as well as scoring systems. Scoring systems and cut points vary with the type of neoplasm being treated. Cytology specimens from the lung, head and neck and melanomas can all be used for PD-L1 testing with good agreement with corresponding histology specimens.

Methods for assessment of the tumour microenvironment and immune interactions in non-small cell lung cancer. A narrative review

Non-small cell lung cancer (NSCLC) is one of the leading causes of cancer death worldwide. Immunotherapy with immune checkpoint inhibitors (ICI) has significantly improved outcomes in some patients, however 80-85% of patients receiving immunotherapy develop primary resistance, manifesting as a lack of response to therapy. Of those that do have an initial response, disease progression may occur due to acquired resistance. The make-up of the tumour microenvironment (TME) and the interaction between tumour infiltrating immune cells and cancer cells can have a large impact on the response to immunotherapy. Robust assessment of the TME with accurate and reproducible methods is vital to understanding mechanisms of immunotherapy resistance. In this paper we will review the evidence of several methodologies to assess the TME, including multiplex immunohistochemistry, imaging mass cytometry, flow cytometry, mass cytometry and RNA sequencing.

Program death ligand-1 immunocytochemistry in lung cancer cytological samples: A systematic review

In this era of personalized medicine, targeted immunotherapies like immune checkpoint inhibitors (ICI) blocking the programmed death‐1 (PD‐1)/program death ligand‐1 (PD‐L1) axis have become an integral part of treating advanced stage non‐small cell lung carcinoma (NSCLC) and many other cancer types. Multiple monoclonal antibodies are available commercially to detect PD‐L1 expression in tumor cells by immunohistochemistry (IHC). As most clinical trials initially required tumor biopsy for PD‐L1 detection by IHC, many of the currently available PD‐1/PD‐L1 assays have been developed and validated on formalin fixed tissue specimens. The majority (>50%) of lung cancer cases do not have a surgical biopsy or resection specimen available for ancillary testing and instead must rely primarily on fine needle aspiration biopsy specimens for diagnosis, staging and ancillary tests. Review of the literature shows multiple studies exploring the feasibility of PD‐L1 IHC on cytological samples. In addition, there are studies addressing various aspects of IHC validation on cytology preparations including pre‐analytical (e.g., different fixatives), analytical (e.g., antibody clone, staining platforms, inter and intra‐observer agreement, cytology‐histology concordance) and post‐analytical (e.g., clinical outcome) issues. Although promising results in this field have emerged utilizing cytology samples, many important questions still need to be addressed. This review summarizes the literature of PD‐L1 IHC in lung cytology specimens and provides practical tips for optimizing analysis.

Keratin 17 testing in pancreatic cancer needle aspiration biopsies predicts survival

BACKGROUND

Although pancreatic ductal adenocarcinoma (PDAC) has one of the lowest 5-year survival rates of all cancers, differences in survival exist between patients with clinically identical characteristics. The authors previously demonstrated that keratin 17 (K17) expression in PDAC, measured by RNA sequencing or immunohistochemistry (IHC), is an independent negative prognostic biomarker. Only 20% of cases are candidates for surgical resection, but most patients are diagnosed by needle aspiration biopsy (NAB). The aims of this study were to determine whether there was a correlation in K17 scores detected in matched NABs and surgical resection tissue sections and whether K17 IHC in NAB cell block specimens could be used as a negative prognostic biomarker in PDAC.

METHODS

K17 IHC was performed for a cohort of 70 patients who had matched NAB cell block and surgical resection samples to analyze the correlation of K17 expression levels. K17 IHC was also performed in cell blocks from discovery and validation cohorts. Kaplan-Meier and Cox proportional hazards regression models were analyzed to determine survival differences in cases with different levels of K17 IHC expression.

RESULTS

K17 IHC expression correlated in matched NABs and resection tissues. NAB samples were classified as high for K17 when ≥80% of tumor cells showed strong (2+) staining. High-K17 cases, including stage-matched cases, had shorter survival.

CONCLUSIONS

K17 has been identified as a robust and independent prognostic biomarker that stratifies clinical outcomes for cases that are diagnosed by NAB. Testing for K17 also has the potential to inform clinical decisions for optimization of chemotherapeutic interventions.

Molecular cytology of the respiratory tract and pleura

There is growing evidence that molecular testing is feasible on all types of cytological preparation, which is fortunate as more diagnostic markers and biomarkers for targeted therapies are discovered for use in pulmonary and pleural malignancies. In this article we will discuss the pre-analytic, analytic, and post-analytic (interpretive) considerations for successful implementation of molecular tests for diagnostic and predictive markers in respiratory and pleural cytology. The vast majority of laboratories are familiar with, and have validated their molecular protocols for, formalin-fixed paraffin-embedded surgical specimens, which are not directly applicable to cytology specimens. Thus, rigorous validation must be performed for each type of fixative and cytology preparation before it is implemented in the clinical setting.

PD-L1 Testing in Cytological Non-Small Cell Lung Cancer Specimens: A Comparison with Biopsies and Review of the Literature

INTRODUCTION

Programmed death-ligand 1 (PD-L1) expression is used for treatment prediction in non-small cell lung cancer (NSCLC). While cytology may be the only available material in the routine clinical setting, testing in clinical trials has mainly been based on biopsies.

METHODS

We included 2 retrospective cohorts of paired, concurrently sampled, cytological specimens and biopsies. Also, the literature on PD-L1 in paired cytological/histological samples was reviewed. Focus was on the cutoff levels ≥1 and ≥50% positive tumor cells.

RESULTS

Using a 3-tier scale, PD-L1 was concordant in 40/47 (85%) and 66/97 (68%) of the paired NSCLC cases in the 2 cohorts, with kappa 0.77 and 0.49, respectively. In the former cohort, all discordant cases had lower score in cytology. In both cohorts, concordance was lower in samples from different sites (e.g., biopsy from primary tumor and cytology from pleural effusion). Based on 25 published studies including about 1,700 paired cytology/histology cases, the median (range) concordance was 81-85% (62-100%) at cutoff 1% for a positive PD-L1 staining and 89% (67-100%) at cutoff 50%.

CONCLUSIONS

The overall concordance of PD-L1 between cytology and biopsies is rather good but with significant variation between laboratories, which calls for local quality assurance.

Integrating endobronchial ultrasound bronchoscopy with molecular testing of immunotherapy biomarkers in non-small cell lung cancer

Immunotherapy has transformed treatment of advanced non-small-cell lung cancer (NSCLC) patients leading to remarkable long-term survival benefit. However, only about 20% of advanced NSCLC patients typically respond to immune checkpoint inhibitors (ICIs) that target the PD-1/PD-L1 pathway. The only validated biomarker for ICI therapy is the PD-L1 immunohistochemistry (IHC) test, which is considered an imperfect assay due to several variables including availability and integrity of tumour tissue, variability in staining/scoring techniques and heterogeneity in PD-L1 protein expression within and across tumour biopsies. Herein, we discuss integrating minimally invasive EBUS bronchoscopy procedures with novel molecular approaches to improve accuracy and sensitivity of PD-L1 testing. EBUS guided bronchoscopy facilitates repeated sampling of tumour tissue to increase the probability of detecting PD-L1 positive tumours. Since intra-tumoural PD-L1 (CD274) copy number is reported to be less heterogeneous than PD-L1 protein detection, quantifying PD-L1 transcript levels may increase detection of PD-L1 positive tumours. PD-L1 transcript levels show excellent concordance with PD-L1 IHC scoring and multiplex digital droplet PCR (ddPCR) assays that quantify absolute PD-L1 transcript copy number have been developed. ddPCR can also be automated for high throughput detection of low abundant variants with excellent sensitivity and accuracy to improve the broader application of diagnostic cut-off values. Optimizing diagnostic workflows that integrate optimal EBUS bronchoscopy procedures with emerging molecular ICI biomarker assays may improve the selection criteria for ICI therapy benefit.

PD-L1 and beyond: Immuno-oncology in cytopathology

Over the past decade, immunotherapy has emerged as one of the most promising cancer treatments. Several monoclonal antibodies targeting the programmed death 1 (PD-1)/ programmed death ligand-1 (PD-L1) pathway have been integrated into standard-of-care treatments for a wide range of cancer types. Although all the available PD-L1 immunohistochemistry (IHC) assays have been developed on formalin-fixed histological specimens, a growing body of research has recently suggested the feasibility of PD-L1 testing on cytological samples. Although promising results have been reported, several important issues still need to be addressed. Among these are pre-analytical issues, cyto-hystological correlation, and inter-observer agreement. This review will briefly summarise the knowledge gaps and future directions of cytopathology in the immuno-oncology scenario.

Programmed death ligand-1 (PD-L1) as a predictive marker for immunotherapy in solid tumours: a guide to immunohistochemistry implementation and interpretation

Immunotherapy with checkpoint inhibitors is well established as an effective treatment for non-small cell lung cancer and melanoma. The list of approved indications for treatment with PD-1/PD-L1 checkpoint inhibitors is growing rapidly as clinical trials continue to show their efficacy in patients with a wide range of solid tumours. Clinical trials have used a variety of PD-L1 immunohistochemical assays to evaluate PD-L1 expression on tumour cells, immune cells or both as a potential biomarker to predict response to immunotherapy. Requests to pathologists for PD-L1 testing to guide choice of therapy are rapidly becoming commonplace. Thus, pathologists need to be aware of the different PD-L1 assays, methods of evaluation in different tumour types and the impact of the results on therapeutic decisions. This review discusses the key practical issues relating to the implementation of PD-L1 testing for solid tumours in a pathology laboratory, including evidence for PD-L1 testing, different assay types, the potential interchangeability of PD-L1 antibody clones and staining platforms, scoring criteria for PD-L1, validation, quality assurance, and pitfalls in PD-L1 assessment. This review also explores PD-L1 IHC in solid tumours including non-small cell lung carcinoma, head and neck carcinoma, triple negative breast carcinoma, melanoma, renal cell carcinoma, urothelial carcinoma, gastric and gastroesophageal carcinoma, colorectal carcinoma, hepatocellular carcinoma, and endometrial carcinoma. The review aims to provide pathologists with a practical guide to the implementation and interpretation of PD-L1 testing by immunohistochemistry.

Safe performance of diagnostic bronchoscopy/EBUS during the SARS-CoV-2 pandemic

The SARS‐CoV‐2 pandemic is unprecedented in our professional lives and much effort and resources will be devoted to care of patients (and HCW) affected by this illness. We must also continue to aim for the same standard of care for our non‐COVID respiratory patients, while minimizing risks of infection transmission to our colleagues. This commentary addresses the key paired issues of minimizing performance of diagnostic/staging bronchoscopy in patients with suspected/known lung cancer while maximizing the safety of the procedure with respect to HCW transmission of COVID‐19.