Immunohistochemistry for predictive biomarkers in non-small cell lung cancer

Abstract

In the era of targeted therapy, predictive biomarker testing has become increasingly important for non-small cell lung cancer. Of multiple predictive biomarker testing methods, immunohistochemistry (IHC) is widely available and technically less challenging, can provide clinically meaningful results with a rapid turn-around-time and is more cost efficient than molecular platforms. In fact, several IHC assays for predictive biomarkers have already been implemented in routine pathology practice. In this review, we will discuss: (I) the details of anaplastic lymphoma kinase (ALK) and proto-oncogene tyrosine-protein kinase ROS (ROS1) IHC assays including the performance of multiple antibody clones, pros and cons of IHC platforms and various scoring systems to design an optimal algorithm for predictive biomarker testing; (II) issues associated with programmed death-ligand 1 (PD-L1) IHC assays; (III) appropriate pre-analytical tissue handling and selection of optimal tissue samples for predictive biomarker IHC.

Keywords: Anaplastic lymphoma kinase (ALK); immunohistochemistry (IHC); non-small cell lung cancer (NSCLC); predictive biomarker; programmed death-ligand 1 (PD-L1); proto-oncogene tyrosine-protein kinase ROS (ROS1).

Figure 1

ALK FISH and IHC. (A) An image of ALK FISH from a patient with metastatic lung adenocarcinoma who responded to crizotinib demonstrating scattered red and green signal pairs with less than two-signal diameter distance from each other (arrows) interpreted as negative (×1,000); (B) IHC for ALK (the clone 5A4) from the same tumor exhibiting cytoplasmic staining in the vast majority of the tumor cells (×200). FISH, fluorescence in situ hybridization.

Figure 2

IHC for ROS1. (A) A ROS1-rearranged lung adenocarcinoma with cytoplasmic staining of various intensities in the vast majority of the tumor cells (×200); (B) scattered tumor cells with weak cytoplasmic staining (arrows) seen in a case with NSCLC that is negative for a ROS1 gene rearrangement (×400); (C) an example of ROS1 wild type invasive mucinous adenocarcinoma demonstrating weak cytoplasmic staining in the majority of the tumor cells (×200); (D) reactive pneumocytes (arrows) and alveolar macrophages (arrowhead) with weak to moderate cytoplasmic staining of ROS1 in the background of tumor cells that are completely negative for the expression (×400).

Figure 3

IHC for PD-L1. (A,B) Examples of squamous cell carcinomas with PD-L1 membranous staining of various intensities on 90% and 10% of the tumor cells, respectively (×200); (C,D) a cell block specimen with non-small cell carcinoma, favor squamous cell carcinoma, exhibiting PD-L1 membranous staining on 50% of tumor cells (C, ×100; D, ×400). PD-L1 IHC was performed using the clone E1L3N with Leica Bond III autostainer in all three cases.