Immunocytochemistry for predictive biomarker testing in lung cancer cytology

Abstract

With an escalating number of predictive biomarkers emerging in non-small cell lung carcinoma (NSCLC), immunohistochemistry (IHC) is being used as a rapid and cost-effective tool for the screening and detection of many of these markers.In particular, robust IHC assays performed on formalin-fixed, paraffin-embedded (FFPE) tumor tissue are widely used as surrogate markers for ALK and ROS1 rearrangements and for detecting programmed death ligand 1 (PD-L1) expression in patients with advanced NSCLC; in addition, they have become essential for treatment decisions. Cytology samples represent the only source of tumor in a significant proportion of patients with inoperable NSCLC, and there is increasing demand for predictive biomarker testing on them. However, the wide variation in the types of cytology samples and their preparatory methods, the use of alcohol-based fixatives that interfere with immunochemistry results, the difficulty in procurement of cytology-specific controls, and the uncertainty regarding test validity have resulted in underutilization of cytology material for predictive immunocytochemistry (ICC), and most cytopathologists limit such testing to FFPE cell blocks (CBs). The purpose of this review is to: 1) analyze various preanalytical, analytical, and postanalytical factors influencing ICC results; 2) discuss measures for validation of ICC protocols; and 3) summarize published data on predictive ICC for ALK, ROS1, EGFR gene alterations and PD-L1 expression on lung cancer cytology. Based on our experience and from a review of the literature, we conclude that cytology specimens are in principal suitable for predictive ICC, but proper optimization and rigorous quality control for high-quality staining are essential, particularly for non-CB preparations.

Insulinoma‐associated protein 1 is a robust nuclear immunostain for the diagnosis of small cell lung carcinoma in cytology smears

“…ICC, especially on alcohol‐fixed cytology preparations, may demonstrate discordant staining results with IHC protocols that are standardized for formalin‐fixed tissue and requires careful validation . Alcohol‐fixed smears and liquid‐based cytology preparations have been previously used for INSM1 ICC in a small study on pancreatic NE tumors in which all 14 NE tumors of different grades demonstrated strong positivity for INSM1, a finding that is concordant with the 100% sensitivities reported with INSM1 IHC for pancreatic NE tumors in other studies .…”

“…3,5,6,[8][9][10][11] ICC, especially on alcohol-fixed cytology preparations, may demonstrate discordant staining results with IHC protocols that are standardized for formalin-fixed tissue and requires careful validation. 18 Alcohol-fixed smears and liquid-based cytology preparations have been previously used for INSM1 ICC in a small study on pancreatic NE tumors in which all 14 NE tumors of different grades demonstrated strong positivity for INSM1, 16 a finding that is concordant with the 100% sensitivities reported with INSM1 IHC for pancreatic NE tumors in other studies. 6 Among previous ICC studies on SCLC, Rodriguez et al 11 and Doxtader and Mukhopadhyay 5 both reported 100% concordance between IHC and ICC in 4 and 20 paired samples, respectively, in which the former performed ICC on formalin-fixed CBs and the latter on PreserveCyt-fixed Cellient CBs.…”

Predictive molecular pathology of lung cancer in Germany with focus on gene fusion testing: Methods and quality assurance

“…A discussion of all of these variables would be beyond the scope of this review, but a detailed description of all factors influencing immunocytochemistry testing can be found in the expert opinion of the International Association for the Study of Lung Cancer Pathology Committee. 64 The major advantage of IHC and ISH is that all fusion events can be detected independently from the fusion partner. Both methods are currently standard in most pathology laboratories and require little technical expertise.…”

Non–small cell lung cancer predictive biomarker testing via immunocytochemistry: Ways of future past?

“…In this issue of Cancer Cytopathology , Jain et al, as part of the International Association for the Study of Lung Cancer (IASLC) Pathology Committee, perform a deep dive into the topic of immunocytochemistry (ICC) for predictive biomarker testing in NSCLC. This work serves as a complementary piece to the recently published review by the same group covering the best practice recommendations for IHC in the diagnostic workup of lung cancer .…”

“…Given the backdrop of rapid change in thoracic oncology and resulting increased testing complexity in this era of personalized medicine, it behooves the cytopathologist to actively participate in a process that has been described as “personalized sample management.” The tumor cell quality, quantity, and purity can greatly vary from specimen to specimen. When considering relevant clinicopathologic features as well as the medical urgency dictated by the clinical status of the patient, the cytopathologist as part of the clinical care team is best situated to enter into discussions with the oncologist to decide if and how to deviate from standard testing algorithms, for instance deciding when to use focused biomarker ICC testing as outlined in the accompanying paper by Jain et al…”