Immunocytochemistry: an indispensable technique in routine cytology

Neutrophil-related IL1R2 gene predicts the occurrence and early progression of myocardial infarction

Introduction

Myocardial infarction (MI) is a leading cause of death worldwide. Immune cells play a significant role in the MI development. This study aims to identify a marker related to neutrophil for the diagnosis and early progression of MI.

Methods

Key genes were screened using three machine learning algorithms to establish a diagnostic model. A gene associated with the early progression of MI was identified based on single cell RNA sequencing data. To further validate the predictive value of the gene, the mouse models of MI were constructed. Immunofluorescence (IF) analysis demonstrated the co-expression of the gene with neutrophils. Immunohistochemistry (IHC) was performed to validate the role of the gene in the progression of MI.

Results

Neutrophils were identified and verified as the key infiltrating immune cells (IICs) involved in the onset of MI. A diagnostic panel with superior performance was developed using five key genes related to neutrophils in MI (AUC = 0.887). Among the panel, IL1R2 was found to early phase of MI, which was further corroborated by IHC in mouse models of MI.

Conclusions

This study suggests that IL1R2, which is specific to neutrophils, can predict the diagnosis and early progression of MI, providing new insights into the clinical management of MI.

Statistical analysis of spatial patterns in tumor microenvironment images

Advances in tissue labeling, imaging, and automated cell identification now enable the visualization of immune cell types in human tumors. However, a framework for analyzing spatial patterns within the tumor microenvironment (TME) is still lacking. To address this, we develop Spatiopath, a null-hypothesis framework that distinguishes statistically significant immune cell associations from random distributions. Using embedding functions to map cell contours and tumor regions, Spatiopath extends Ripley's K function to analyze both cell-cell and cell-tumor interactions. We validate the method with synthetic simulations and apply it to multi-color images of lung tumor sections, revealing significant spatial patterns such as mast cells accumulating near T cells and the tumor epithelium. These patterns highlight differences in spatial organization, with mast cells clustering near the epithelium and T cells positioned farther away. Spatiopath enables a better understanding of immune responses and may help identify biomarkers for patient outcomes.

Unraveling microglial spatial organization in the developing human brain with DeepCellMap, a deep learning approach coupled with spatial statistics

Mapping cellular organization in the developing brain presents significant challenges due to the multidimensional nature of the data, characterized by complex spatial patterns that are difficult to interpret without high-throughput tools. Here, we present DeepCellMap, a deep-learning-assisted tool that integrates multi-scale image processing with advanced spatial and clustering statistics. This pipeline is designed to map microglial organization during normal and pathological brain development and has the potential to be adapted to any cell type. Using DeepCellMap, we capture the morphological diversity of microglia, identify strong coupling between proliferative and phagocytic phenotypes, and show that distinct spatial clusters rarely overlap as human brain development progresses. Additionally, we uncover an association between microglia and blood vessels in fetal brains exposed to maternal SARS-CoV-2. These findings offer insights into whether various microglial phenotypes form networks in the developing brain to occupy space, and in conditions involving haemorrhages, whether microglia respond to, or influence changes in blood vessel integrity. DeepCellMap is available as an open-source software and is a powerful tool for extracting spatial statistics and analyzing cellular organization in large tissue sections, accommodating various imaging modalities. This platform opens new avenues for studying brain development and related pathologies.

Role of Immunocytochemistry in the Cytological Diagnosis of Mesothelioma

BACKGROUND

Mesothelioma is an aggressive malignancy of the serosal surfaces with very poor prognosis. It traditionally manifests in older patients and at an advanced stage which results in minimal improvement in prognosis despite the recent advances in management. Early detection would therefore significantly impact management and potentially improve survival. Mesothelioma frequently presents with recurrent effusions, posing cytology as the initial procedure in the workup. A definitive diagnosis would not only spare the patients additional diagnostic procedures but also potentially afford them an opportunity for early surgical intervention and therapy.

SUMMARY

In this article, we review the role of immunocytochemistry (ICC) in the workup of mesothelioma. The various ICC markers to confirm or rule out mesothelial lineage are reviewed. In addition, newly introduced molecular surrogates that confirm the malignant nature of the mesothelial cells and support a definitive diagnosis of mesothelioma are discussed. We also briefly discuss the theranostic implications of such markers and potential impact of such recent advances on the cytological diagnosis and reporting of mesothelioma.

KEY MESSAGES

The cytological diagnosis of mesothelioma no longer requires the extensive expertise in morphological analysis and can be offered based on supporting ICC that confirms the mesothelial lineage and malignant nature of the cells.

Practical issues related to immunocytochemistry on cytological smears: Tips and recommendations

OBJECTIVE

Immunocytochemistry (ICC) is essential for enhancing diagnostic accuracy and identifying markers for diagnosis, prognosis and targeted therapies. While cell blocks (CBs) are preferred for standardization and optimized staining, cytological smears are an alternative when CBs are unavailable. However, the literature on ICC protocols for smears is sparse. This review addresses preparation, fixation and protocols for nuclear and cytoplasmic antibodies on smears, drawing from our laboratory's experience.

METHODS

We reviewed procedures for ICC on cytological smears using existing literature and practical insights from our laboratory.

RESULTS

Commercially available antibodies were found to be reliable for ICC on smears if specimens are properly prepared and fixed. Protocols developed in our laboratory maintained antigenicity and provided clear staining results.

CONCLUSIONS

Although ICC on CBs is the gold standard for standardization, cytological smears are a viable alternative when CBs are unavailable. Success in ICC on smears depends on proper preparation and fixation. This review offers practical protocols and insights to help laboratories optimize ICC on cytological smears. Further research and standardization are necessary to enhance reproducibility and reliability of ICC on smears. The practical information provided is based on personal experience in our laboratory.

Quality Assurance in Immunocytochemistry: A Review and Practical Considerations

BACKGROUND

Cytological samples play a critical role in diagnosing advanced-stage tumors and those arising in difficult-to-reach anatomical sites such as the pancreatobiliary tract, lung, thyroid, suprarenal, pelvis, and others such as salivary glands. These samples are often the only available material for accurate diagnosis and for performing ancillary studies, such as immunocytochemistry (ICC) or the detection of molecular biomarkers.

SUMMARY

While the use of immunohistochemistry is well established and standardized on formalin-fixed-paraffin-embedded histological tissue, in cytological samples, it presents unique challenges. Methods used for obtaining and processing these specimens are complex and are not standardized among laboratories. Moreover, there is also diversity in the types of cytological samples potentially suitable for ICC.

KEY MESSAGES

This review explores the current landscape of ICC practices in European and North American laboratories, highlighting variability in methods and the need for standardization to ensure reliable results and reproducibility of ICC on cytological 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.

Cytochemical and Histochemical Staining with Peptide Antibodies

Peptide antibodies are particularly useful for immunocytochemistry (ICC) and immunohistochemistry (IHC), where antigens may denature due to fixation of tissues and cells. Peptide antibodies can be made to any defined sequence, including unknown putative proteins and posttranslationally modified sequences. Moreover, the availability of large amounts of the antigen (peptide) allows inhibition/absorption controls, which are important in ICC/IHC, due to the many possibilities for false-positive reactions caused by immunoglobulin Fc receptors, nonspecific reactions and cross-reactivity of primary and secondary antibodies with other antigens and endogenous immunoglobulins, respectively. Here, simple protocols for ICC and IHC are described together with recommendations for appropriate controls.

Visualizing neutrophil extracellular traps in septic equine synovial and peritoneal fluid samples using immunofluorescence microscopy

Septic synovitis and peritonitis are routinely diagnosed in horses based on clinical examination findings and laboratory assessment of synoviocentesis and abdominocentesis samples, respectively. Diagnosis is difficult in some cases because of an overlap in laboratory results for septic and non-septic inflammation. Neutrophil extracellular trap (NET) formation is part of the innate immune response against pathogens. Identifying and quantifying NETs, which have not been explored in clinical samples from horses with septic synovitis and peritonitis, to our knowledge, may be helpful in detecting infectious processes. Our main objective was to determine whether NETs could be visualized in septic equine synovial and peritoneal fluid cytology samples using immunofluorescence with antibodies against citrullinated histone H3 (Cit-H3) and myeloperoxidase (MPO). We analyzed 9 synovial and 4 peritoneal fluid samples. NET percentages were quantified using a simple counting technique, which is suitable for high-quality, well-preserved, and stained cytospin smears. NETs were evident in all septic samples and were absent in a non-septic sample; NETs were better visualized with Cit-H3 than with MPO immunolabeling. Overall, we believe that there is the potential for NETs and associated markers to be used to investigate and understand septic inflammation in horses.

DNA image cytometry ploidy analysis technique improves the detection rate of pleural effusion cytology

OBJECTIVE

To explore the clinical diagnostic value of DNA image cytometry (DNA-ICM) ploidy analysis in malignant pleural effusion cancer screening, this study analyzed the effect of exfoliated cell smears (ECSs), cell blocks (CBs), and immunochemistry.

METHOD

A total of 830 cases of pleural effusion were considered for the DNA-ICM ploidy analysis. The ECSs were centrifuged, the CBs were formed, and the DNA-ICM ploidy analysis was carried out in the diagnosis of malignant pleural effusion. Immunochemistry and biopsy was applied to differentiate between benign and malignant pleural effusion and to determine the source of the latter. The sensitivity and specificity differences between the three methods alone and in combination were compared.

RESULTS

The sensitivity of the DNA-ICM, ECS, and CB methods was 96.28%, 94.93%, and 95.95%, respectively, and the specificity of each method was 86.52%, 87.08%, and 86.14%, respectively. The sensitivity and specificity of the combined diagnosis method were 99.32% and 75.09%, respectively. Among the 22 cases diagnosed as positive in the DNA-ICM ploidy analysis but negative in the ECS and CB analyses, four cases were diagnosed as positive by comprehensive clinical diagnosis.

CONCLUSION

The sensitivity and specificity of DNA-ICM ploidy analysis are high; the positive detection rate of pleural fluid cytology is effectively increased, and the missed detection rate of cell pathologies is effectively reduced. The combination of the three methods significantly improves the specificity and sensitivity of the diagnosis of malignant pleural effusion, and immunochemistry with CBs can be used to accurately analyze the primary tumor site.

Molecular/biomarker testing in lung cytology: A practical approach

The increasing comprehension of molecular mechanisms underlying lung cancer and the discovery of targetable genomic alterations has dramatically change the pathological approach to lung cancer, especially non-small cell lung cancer (NSCLC). This unstoppable knowledge has taken pathologists to the leading front on lung cancer management. This is especially relevant in the world of cytopathology where "doing more with less" is a daily challenge. Nowadays with a growing number of predictive biomarkers needed to manage patients with NSCLC, there has been a paradigm shift in care and handling of diagnostic samples. One of the main emphasis and interest relies on the utilization of cytologic samples and small biopsies for not only diagnostic purposes but also for ancillary testing. Moreover, lung cytopathology is in continuous evolutions with implementation of new diagnostic techniques, new tools, and facing new challenges. The goal of this paper will be to provide the reader with the necessary concepts than can be used to exploit the cytological samples in order to use these samples for comprehensive diagnosis and relevant ancillary testing purposes.

Doing more with less: multiple uses of a single slide in veterinary cytology. A practical approach

Veterinary cytology faced a remarkable evolution in the last 15 years, in part due to increase recognition of the advantages of the cytology by veterinary clinicians. Simultaneously, there has been a growing awareness by the owners about the importance of a complete diagnostic workup aimed at defining a proper treatment protocol. With the extended use of cytology, challenging diagnostic cases are more frequent, and more clinically useful answers are requested. In this scenario, the use of cytology specimens to perform ancillary techniques is a valid approach. Rather than being simply archived, cytology slides can be a valuable source and a good platform to carry out cytochemistry, immunocytochemistry, and molecular techniques. Therefore, several diagnostic techniques can be applied in tiny samples, thus following the "doing more with less" principle. The aim of this approach is to refine the cytologic diagnosis and provide additional prognostic and therapeutic information. Herein, we detailed this principle in veterinary cytology and reviewed the use of cytology specimens for ancillary techniques as a single procedure, i.e., using the whole slide, or multiple procedures, i.e., multiple procedures applied in the same slide.

Site-Specific Fluorescent Labeling, Single-Step Immunocytochemistry, and Delivery of Nanobodies into Living Cells

The smallest natural antibody fragments currently available are single-domain antibodies obtained from camelid species and sharks (variable new antigen receptors). These molecules consist of a single amino acid chain of ~120 amino acids that adopts a typical immunoglobulin fold. Single-domain antibodies (nanobodies) are monovalent and can be isolated from immunized animals, from naïve libraries, or from synthetic libraries. Importantly, their complete DNA sequences are readily obtained by default, which greatly facilitates their rapid manipulation for various applications. Here, a PCR-based protocol for inserting a sortase A recognition sequence at the carboxy-terminus of a nanobody is described. Subsequently, a sortase A-catalyzed biochemical reaction results in tagging of the nanobody with a short carboxy-terminal amino acid sequence that carries a non-canonical residue (propargyl glycine). This allows click chemistry to be performed with an azido-derivatized fluorophore, with the ensuing fluorescent nanobody being covalently and site-specifically labeled. The labeled nanobody can be used directly for immunocytochemistry, omitting the classical secondary antibody step. Also described are methods for delivery of fluorescent nanobodies into the cytoplasm of mammalian cells by photoporation, a very low-toxicity approach involving laser light and graphene quantum dots. The combined protocol embodies a novel route for studying protein function in living cells at high resolution.

Influence of deep-freezing and MGG staining on DNA and RNA quality in different types of lung adenocarcinoma cytological smears

BACKGROUND

Preserving the optimal quality of DNA and RNA is mandatory for molecular testing in lung adenocarcinoma cytological smears (LACSs).

METHODS

DNA and RNA were isolated from 90 frozen unstained and 46 May Grünwald Giemsa (MGG) stained LACSs prepared from bronchial washing (BW), bronchial brushing (BB), and pleural effusion (PE) samples during 3 years. Concentrations of nucleic acids in all LACSs were assessed by spectrophotometric analysis. Fragmentation of DNA and RNA was determined by PCR amplification of selected genes. Amplicons of 100, 200, 300, 400, and 600 bp were used for DNA and 108 bp-long HPRT1 transcript fragment for RNA fragmentation analysis.

RESULTS

Among 90 frozen LACSs, significantly lower DNA concentrations of BB and RNA concentrations of BW samples frozen for 6-10 months were observed in comparison with samples frozen for longer periods (p < .05). Among 46 paired LACSs, 44 (95.7%) frozen and 15 (32.6%) MGG-stained samples showed 600 bp-long DNA amplicons. Statistically significant difference (p < .05) in the fragmentation of DNA between frozen and MGG-stained LACSs was observed (p < .05), with DNA being less fragmented in frozen LACSs. In addition, 33 (71.7%) frozen and 36 (78.2%) MGG-stained LASCs showed HPRT1 gene amplicon of 108 bp. RNA was less fragmented in 3-year old MGG-stained samples than in LACSs frozen for 3 years.

CONCLUSION

DNA and RNA extracted from frozen and MGG-stained LACSs showed different results depending on the time of storage and/or type of samples, but in general all samples had adequate quantity and quality for downstream molecular testing.

Accuracy of fine-needle aspiration of lymph nodes: A cancer center's experience

INTRODUCTION

Lymph node fine needle aspiration (LN-FNA) is a minimally invasive method of evaluating lymphadenopathy. Nonetheless, its use is not widely accepted due to the lack of guidelines and a cytopathological categorisation that directly relates to management. We report our experience with LN FNA at a large Cancer Center in Latin America.

METHODS

We retrospectively collected cytological cases of lymph node FNA from the department of pathology at AC Camargo Cancer Center performed over a 2-year period. Data extracted included LN location, age, sex and final cytological diagnosis. Patients that had undergone neoadjuvant chemotherapy and/or cases for which the surgery specimen location was not clearly reported were excluded. For those cases with surgical reports, risk of malignancy was calculated for each diagnostic category, along with overall performance of cytology. False positive cases were reviewed to assess any possible misinterpretation or sampling errors.

RESULTS

A total of 1730 LN-FNA were distributed as follows: 62 (3.5%) non-diagnostic (ND); 1123 (64.9%) negative (NEG), 19 (1.1%) atypical (ATY), 53 (3.1%) suspicious for malignancy (SUS), and 473 (27.3%) positive (POS). Surgical reports were available for 560 cases (32.4%). Risk of malignancy (ROM) for each category was 33.3% for ND, 29.9% for NEG, 25% for ATY, 74.2% for SUS and 99.6% for POS. Overall sensitivity, specificity, negative predictive value (NPV) and positive predictive value (PPV) were 78.5%, 99.4%, 70.2% and 99.6%, respectively.

CONCLUSION

Lymph node FNA is a very specific and accurate exam, which is reliable in the detection of lymph node metastasis and other causes of lymphadenopathy.

Molecular Testing on Cytology for Gene Fusion Detection

Cytology samples are suitable for the study of genotypic and phenotypic changes observed in different tumors. Being a minimally invasive technique, cytology sampling has been used as an acceptable alternative to track the alterations associated with tumor progression. Although the detection of gene mutations is well-established on cytology, in the last few years, gene fusion detections are becoming mandatory, especially in some tumor types such as lung cancer. Different technologies are available such as immunocytochemistry, fluorescence in situ hybridization, reverse transcription-polymerase chain reaction, and massive parallel sequencing approaches. Considering that many new drugs targeted fusion proteins, cytological samples can be of use to detect gene fusions in solid and lymphoproliferative tumor patients. In this article, we revised the use of several techniques utilized to check gene fusions in cytological material.

Immunocytochemistry for diagnostic cytopathology-A practical guide

Cytological specimens, which are obtained by minimally invasive methods, are an excellent source of diagnostic material. Sometimes they are the only material available for diagnosis as well as for prognostic/predictive markers. When cytomorphology is not straightforward, ancillary tests may be required for a definitive diagnosis to guide clinical management. Immunocytochemistry (ICC) is the most common and practical ancillary tool used to reach a diagnosis when cytomorphology is equivocal, to differentiate entities with overlapping morphological features, and to determine the cell lineage and the site of origin of a metastatic neoplasm. Numerous immunomarkers are available, and some are expressed in multiple neoplasms. To rule out entities within a differential diagnosis, the use of more than one marker, sometimes panels, is necessary. ICC panels for diagnostic purposes should be customised based on the clinical context and cytomorphology, and the markers should be used judiciously to preserve material for additional tests for targeted therapies in the appropriate setting. This review offers a practical guide for the use of ICC for diagnostic cytopathology, covering the most commonly encountered non-hematolymphoid diagnostic scenarios in various body sites.

Immunochemistry in the work-up of mesothelioma and its differential diagnosis and mimickers

The differential diagnosis in cellular effusions with cytological atypia often includes malignant mesothelioma (MM), reactive mesothelial proliferation, and malignancies of metastatic origin, particularly carcinomas. The International Reporting System for Serous Fluid recently established guidelines for reporting MM. In conjunction with the cytomorphologic evaluation, the role of immunochemistry (IC) was emphasized as a very useful tool in the workup of serous fluids, especially with the availability of novel markers. Utilizing a panel of markers, IC allows the characterization of the cells, whether mesothelial or not, and when mesothelial origin is established, IC can frequently assist in delineating its benign or malignant nature. IC can also confirm metastatic disease, allowing the identification of the primary origin in most cases. This review summarizes the current status of IC and its role in the diagnosis of MM and its differential diagnosis in serous fluids.

Size-Dependent Penetration of Gold Nanoprobes into Fixed Cells

Nanoprobes have been increasingly applied in the biomedical field due to their superior optical, electronic, or magnetic properties. Among the many aspects involved in the interaction between nanoprobes and biospecimens, size plays an essential role. Although the influence of size on their internalization behavior and distribution in live cells has been extensively studied, how does the size affect penetration of nanoprobes into fixed cells remains unknown. We investigate here the influence of size on the penetration behavior of gold nanoprobes into fixed mammalian cells by dark-field microscopy and surface-enhanced Raman scattering (SERS) microspectroscopy. We show that 14, 20, and 29 nm nanoprobes can readily enter into methanol-fixed MCF-7 cells, while 42 and 55 nm nanoprobes cannot cross the cell membrane. For 4% paraformaldehyde-fixed cells, even 14 nm nanoprobes can hardly get into the cells, but after treatment with permeabilization reagents, 14 and 20 nm nanoprobes are permitted to enter the cells. These findings provide important implications in future design of nanoprobes for cellular immunostaining.

Immunocytochemistry of cytology specimens for predictive biomarkers in lung cancer

With a growing number of predictive biomarkers that have emerged in non-small cell lung carcinoma (NSCLC), there has been a paradigm shift in the management of these patients. Of the various predictive biomarker testing methods, immunohistochemistry (IHC) is the most widely available, cost-effective, and commonly used methods. However, most predictive IHC assays are validated primarily on formalin-fixed paraffin-embedded (FFPE) histologic tissue samples and translating these assays to cytologic specimens requires additional and rigorous validation. This is part due to the lack of standardized processing protocols in cytology resulting in a variety of preanalytic variables that can impact the antigenicity of antibodies used for predictive biomarker testing. The review article discusses the various preanalytical and analytical factors that impact immunocytochemistry (ICC) in cytologic specimens and summarizes the current published literature on ALK, ROS1, PD-L1, and other predictive biomarker ICC in cytology.

A Proposal for the Performance, Classification, and Reporting of Lymph Node Fine-Needle Aspiration Cytopathology: The Sydney System

BACKGROUND

The evaluation of lymph nodes (LN) by fine-needle aspiration cytology (FNAC) is routinely used in many institutions but it is not uniformly accepted mainly because of the lack of guidelines and a cytopathological diagnostic classification. A committee of cytopathologists has developed a system of performance, classification, and reporting for LN-FNAC.

METHODS

The committee members prepared a document that has circulated among them five times; the final text has been approved by all the participants. It is based on a review of the international literature and on the expertise of the members. The system integrates clinical and imaging data with cytopathological features and ancillary techniques. The project has received the endorsement and patronage of the International Academy of Cytology and the European Federation of the Cytology Societies.

RESULTS

Clinical, imaging, and serological data of lymphadenopathies, indications for LN-FNAC, technical procedures, and ancillary techniques are evaluated with specific recommendations. The reporting system includes two diagnostic levels. The first should provide basic diagnostic information and includes five categories: inadequate/insufficient, benign, atypical lymphoid cells of undetermined/uncertain significance, suspicious, and malignant. For each category, specific recommendations are provided. The second diagnostic level, when achievable, should produce the identification of specific benign or malignant entities and additional information by utilizing ancillary testing.

CONCLUSION

The authors believe that the introduction of this system for performing and reporting LN-FNAC may improve the quality of the procedure, the report, and the communication between cytopathologists and the clinicians. This system may lead to a greater acceptance and utilization of LN-FNAC and to a better interdisciplinary understanding of the results of this procedure.

Modified Liquid-Based Cytology Technique for Immunocytochemistry in Effusion Specimen

Objective:

Immunocytochemistry (ICC) of serous effusion is an important tool for the diagnosis of benign and malignant cells. Our aim was to develop a modified liquid-based cytological technique for ICC (i.e., a modified LBC).

Methods:

Serous effusions of 110 cases were collected for cytological examination: 50 were negative for malignancy albeit benign mesothelium was found, and 60 were confirmed metastatic adenocarcinoma according to the modified LBC preparation. The latter were stained for EMA, Ber-EP4, Calretinin, and p63 then interpreted by both a cytotechnologist and a pathologist. A comparative analysis of the diagnostic results was conducted.

Results:

The results of the metastatic adenocarcinoma were 100% (60/60) positive for EMA and 91.7% (55/60) positive for Ber-Ep4 but negative for calretinin and p63. Cases negative for malignancy were 100% (50/50) positive for calretinin but negative for carcinoma markers. The difference between ‘positive for metastatic adenocarcinoma’ and ‘negative for malignancy’ in ICC was statistically significant (p < 0.001).

Conclusion:

The current study demonstrated that a panel marker, comprising EMA, Ber-EP4, and calretinin can be used for differentiating between cases of metastatic adenocarcinoma and benign mesothelium. The serous effusion specimen collected by the modified LBC technique is an effective preparation method for ICC.

Ancillary Tests in Breast Cytology: A Practical Guide

Utilization of fine-needle aspiration biopsy (FNAB) cytology for the diagnosis of diseases of the breast has been met with both excitement and uncertainty during the last couple of decades. Presently, FNAB for the diagnosis of primary and metastatic breast lesions is on the rise again. This is probably due to its fast turnaround time, cost efficiency, and minimal invasiveness, characteristics of this sampling modality which are particularly crucial for patients requiring frequent repeat biopsy in the setting of metastatic lesions. In this article, we will briefly review the main modern applications of FNAB of the breast when coupled with contemporary ancillary techniques. Such contemporary ancillary techniques range from classic immunocytochemistry (ICC) to the most modern molecular techniques, particularly next-generation sequencing. Coupled with contemporary ICC and molecular methods, FNAB of the breast can be used for several applications. The applications reviewed in this article include the primary diagnosis of a breast lesion, the identification of the breast as a primary source of a metastatic lesion, the evaluation of breast prognostic/predictive markers, and the tracking of tumor evolution. In our opinion, FNAB of the breast is an ideal sampling method, sharing many of the advantages of truly liquid and of tissue biopsies. Ultimately, we aim at demystifying the complexity of many of the challenges traditionally associated with the application of ancillary techniques to FNAB of the breast and provide insights into some of the most cutting-edge and clinically useful application scenarios.

Immunocytochemistry for predictive biomarker testing in lung cancer cytology

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.

Antigens under cover-The preservation and demasking of selected antigens for successful poststaining immunocytochemistry of effusion, brain smears, and lymph node aspirates

Background

In clinical cytology, the applicability of an ancillary test such as immunocytochemistry is too often limited by low sample volume, poor cell representation, and sample preservation. Diagnosticians often read Romanowsky‐stained cytology, although specific techniques such as immunocytochemistry are often essential for a definitive diagnosis.

Objectives

The goal of the present study aimed to investigate if immunocytochemistry on previously‐stained cytologic specimens was possible. Different pretreatments were examined to determine which treatment preserved antigenicity best.

Methods

One hundred and twenty‐two impression smears and 64 fine‐needle aspirate preparations of brain and lymph nodes were processed and evaluated microscopically. The impact of staining cytologic preparations with a modified Wright's stain, using a destaining method, performing a coverslipping and decoverslipping process, and subjecting smears to a microwave treatment (MWT) were examined for the immunolabeling of selected nuclear, cytoplasmic, and plasmalemmal antigens, as well as intracellular feline coronavirus (FCoV). Biotinylated secondary antibodies were used, and the bound primary antibody was visualized using an ABC amplification kit.

Results

Cellular antigens were reliably detected with immunocytochemistry after smears were stained with a Romansky stain and were coverslipped early after staining and stayed coverslipped until immediately before immunolabeling. The staining intensity reached the same levels as that of the controls if the films underwent MWT in citrate buffer. In contrast, FCoV antigen detection was abolished after any physicochemical interference.

Conclusions

Poststaining immunocytochemistry represents a practical tool for additional investigations on prestained cytologic specimens when searching for cellular antigens. Paired untreated samples should be kept in case the workup requires testing for more vulnerable viral antigens.

Quantifying Podocytes and Parietal Epithelial Cells in Human Urine Using Liquid-based Cytology and WT1 Immunoenzyme Staining

In glomerular disease, podocytes and parietal epithelial cells (PECs) are shed in the urine. Therefore, urinary podocytes and PECs are noninvasive biomarkers of glomerular disease. The purpose of this protocol is to employ immunocytochemistry to detect podocytes and PECs, using the WT1 antibody on liquid-based cytology slides.

Gata3 Immunohistochemical Staining is A Useful Marker for Metastatic Breast Carcinoma in Fine Needle Aspiration Specimens

Aims

The utility of GATA3 immunohistochemistry (IHC) as an aid to the cytological diagnosis of metastatic breast carcinoma in fine needle aspiration (FNA) specimens was investigated.

Materials and Methods

Cell block sections from 111 FNA cases of metastatic malignancy were stained for GATA3, including metastases from 43 breast and 44 nonmammary adenocarcinomas, 19 melanomas, 4 urothelial carcinomas, and 1 thyroid medullary carcinoma. Sites sampled included lymph nodes (87), bone (8), liver (5), lung (6), superficial masses (4), and pelvic mass (1).

Results

Ninety-one percent (39/43) of metastatic breast carcinoma cases were positive for GATA3. All estrogen receptor (ER)-positive were also GATA3 positive cases. The majority (9/14; 64%) of ER-negative and 37% (3/8) of triple-negative cases were positive for GATA3. All nonmammary adenocarcinoma cases were negative with the exception of one case of metastatic pancreatic adenocarcinoma. Metastatic melanoma cases were all negative but 75% (3/4) urothelial carcinomas expressed GATA3.

Conclusions

GATA3 IHC staining is a useful addition to IHC panels for FNA samples in specific settings such as distinguishing metastatic breast from lung carcinoma or melanoma.

Urinary WT1-positive cells as a non-invasive biomarker of crescent formation

OBJECTIVE

The purpose of this study was to assess the relationship between urinary WT1-positive cells (podocytes and active parietal epithelial cells) and WT1-positive cells in renal biopsy to investigate whether urinary WT1-positive cells are useful for detection of crescent formation.

METHODS

Fifty-two patients with kidney disease were investigated (15 cases with crescentic lesions and 37 cases with non-crescentic lesions) for immunoenzyme staining using anti-WT1 antibody for urine cytology and renal biopsy. Numbers of WT1-positive cells in urine and renal biopsy were counted.

RESULTS

There was no correlation between urinary WT1-positive cells and WT1-positive cells in renal biopsy. However, the number of urinary WT1-positive cells in patients with crescentic lesions was significantly higher than in patients with non-crescentic lesions. In addition, the best cut-off value to detect patients with crescentic lesions using urinary was 5 cells/10-mL (area under the concentration-time curve=0.735).

CONCLUSIONS

The results of our study suggest urinary WT1-positive cells can be used to detect patients with crescent formation using 5 cells/10-mL cutoff value. WT1-positive glomerular podocytes and parietal epithelial cells may be shed into urine in active glomerular disease. This study, investigating the relationship between WT1-positive cells in urine and in the renal biopsy found no correlation; however, the results do suggest that, using a cutoff value of 5 cells/10 mL, WT1 positive urinary cells can be used to detect patients with crescent formation.

Quality control for the in-clinic veterinary laboratory and pre-analytic considerations for specialized diagnostic testing

This review, aimed primarily at general practitioners, focuses on quality assurance/quality control principles for all three phases of clinical pathology testing: preanalytic, analytic, and postanalytic. Specific emphasis is placed on the preanalytic phase of diagnostic modalities for identifying neoplastic cells, specifically flow cytometry, PCR for antigen receptor rearrangement, and immunocytochemistry. Recommendations for establishing an in-clinic quality assurance system are provided.

Immunocytochemical and Immunohistochemical Staining with Peptide Antibodies

Peptide antibodies are particularly useful for immunocytochemistry (ICC) and immunohistochemistry (IHC), where antigens may denature due to fixation of tissues and cells. Peptide antibodies can be made to any defined sequence, including unknown putative proteins and posttranslationally modified sequences. Moreover, the availability of large amounts of the antigen (peptide) allows inhibition/adsorption controls, which are important in ICC/IHC, due to the many possibilities for false-positive reactions caused by immunoglobulin Fc receptors, nonspecific reactions, and cross-reactivity of primary and secondary antibodies with other antigens and endogenous immunoglobulins, respectively. Here, simple protocols for ICC and IHC are described together with recommendations for appropriate controls.

Comparison of the Cellient(™) automated cell block system and agar cell block method

OBJECTIVE

To compare the Cellient(TM) automated cell block system with the agar cell block method in terms of quantity and quality of diagnostic material and morphological, histochemical and immunocytochemical features.

MATERIALS AND METHODS

Cell blocks were prepared from 100 effusion samples using the agar method and Cellient system, and routinely sectioned and stained for haematoxylin and eosin and periodic acid-Schiff with diastase (PASD). A preliminary immunocytochemical study was performed on selected cases (27/100 cases). Sections were evaluated using a three-point grading system to compare a set of morphological parameters. Statistical analysis was performed using Fisher's exact test.

RESULTS

Parameters assessing cellularity, presence of single cells and definition of nuclear membrane, nucleoli, chromatin and cytoplasm showed a statistically significant improvement on Cellient cell blocks compared with agar cell blocks (P < 0.05). No significant difference was seen for definition of cell groups, PASD staining or the intensity or clarity of immunocytochemical staining. A discrepant immunocytochemistry (ICC) result was seen in 21% (13/63) of immunostains.

CONCLUSION

The Cellient technique is comparable with the agar method, with statistically significant results achieved for important morphological features. It demonstrates potential as an alternative cell block preparation method which is relevant for the rapid processing of fine needle aspiration samples, malignant effusions and low-cellularity specimens, where optimal cell morphology and architecture are essential. Further investigation is required to optimize immunocytochemical staining using the Cellient method.

Liquid-based cytology in fine-needle aspiration of breast lesions: a review

OBJECTIVE

Fine-needle aspiration (FNA) is a safe and cost-effective technique for the diagnosis of breast lesions, especially when correlated with clinical and imaging studies. However, the success of breast FNA is highly dependent on the adequate preparation of cytological conventional smears (CS). The liquid-based cytology (LBC) technique consists of an automated method for preparing thin-layer cytological samples from cell suspensions collected in alcohol-based preservative. LBC is designed to improve CS by avoiding limiting factors such as obscuring material, air-drying and smearing artifacts.

STUDY DESIGN

We performed a review of the published literature about LBC applied to breast FNA.

RESULTS

LBC preparations of breast aspirates demonstrated better cellular preservation, less cell overlapping and elimination of blood and excessive inflammation compared to CS. Conversely, alterations in architecture and cell morphology as well as loss of myoepithelial cells and stromal elements have been described in LBC specimens, requiring training before applying this technique for diagnosis. Studies have shown a similar accuracy between LBC and CS for the diagnosis of breast lesions. LBC also permits the use of residual material for ancillary tests, which is an important advantage compared to CS.

CONCLUSIONS

LBC can be safely applied to breast FNA, showing a similar diagnostic accuracy to CS.

Immunocytochemical staining of endogenous nuclear proteins with the HIS-1 anti-poly-histidine monoclonal antibody: a potential source of error in His-tagged protein detection

Histidine-tagged proteins are widely used in biochemical studies and frequently detected with antibodies specific for the histidine tag. Immunocytochemistry is widely used in studies with overexpressed proteins to determine cellular localization and in the case of histidine-tagged proteins can be carried out with anti-polyhistidine antibodies. Recent studies have suggested that polyhistidine sequences are present within a small number of human proteins and may direct expression to the nucleus and nuclear speckles compartments of the cell. In this study immunocytochemical staining of human SH-SY5Y neuroblastoma cell lines with the HIS-1 anti-polyhistidine monoclonal antibody were determined. Results showed that the HIS-1 anti-polyhistidine monoclonal antibody stained endogenous nuclear proteins in SH-SY5Y cells. The stained proteins were contained within the nuclear membrane, but were not directly linked to DNA. In a histidine-tagged catalase overexpressing cell line the HIS-1 anti-polyhistidine monoclonal antibody showed nuclear staining, whilst staining with the CAT-505 anti-catalase monoclonal antibody showed primarily cytoplasmic staining. These results suggest that anti-polyhistidine antibody staining shows significant cross-reactivity with endogenous nuclear proteins in SH-SY5Y neuroblastoma cells and may not be suitable for localization studies of histidine-tagged proteins. Immunocytochemical studies with anti-polyhistidine antibodies and localization of histidine-tagged proteins must be confirmed with protein specific antibodies or other methodology.

Role of fine-needle aspiration in the surgical management of pancreatic neuroendocrine tumors: utility and limitations in light of the new World Health Organization classification

CONTEXT

Pancreatic neuroendocrine tumors (Panc-NETs) are rare and tend to get overshadowed by their more prevalent and aggressive ductal adenocarcinoma counterparts. The biological behavior of PancNETs is unpredictable, and thus management is controversial. However, the new World Health Organization classification has significantly contributed to the prognostic stratification of these patients. Concurrently, there have been advances in surgical techniques for benign or low-grade pancreatic tumors. These procedures include minimally invasive and parenchyma-sparing operations such as laparoscopy and enucleation.

OBJECTIVE

To report on the utility and limitations of fine-needle aspiration in the preoperative evaluation and management of PancNETs.

DESIGN

This was a retrospective review of our institutional tumor database from 2002 to 2012. There were 25 cases of PancNETs that were localized and staged by medical imaging and diagnosed by fine-needle aspiration.

RESULTS

Fourteen patients underwent laparotomy, with some requiring only limited surgery; 4 had laparoscopic resections; 4 were serially observed without surgical intervention; and another 3 were inoperable. After a mean follow-up of 37 months, more than half of the patients had no evidence of disease, including most of those who underwent minimally invasive surgery.

CONCLUSIONS

Fine-needle aspiration is a useful diagnostic adjunct to medical imaging in the preoperative evaluation and management of PancNETs. However, there are limitations with regard to grading PancNETs using this technique.

Immunohistochemistry practices of cytopathology laboratories: a survey of participants in the College of American Pathologists Nongynecologic Cytopathology Education Program

CONTEXT

Immunohistochemistry (IHC) is important for cytology but poses special challenges because preanalytic conditions may differ from the conditions of IHC-positive controls.

OBJECTIVE

To broadly survey cytology laboratories to quantify preanalytic platforms for cytology IHC and identify problems with particular platforms or antigens. To discover how validation guidelines for HER2 testing have affected cytology.

DESIGN

A voluntary survey of cytology IHC practices was sent to 1899 cytology laboratories participating in the College of American Pathologists Nongynecologic Cytopathology Education Program in the fall of 2009.

RESULTS

A total of 818 laboratories (43%) responded to the survey by April 2010. Three hundred fourty-five of 791 respondents (44%) performed IHC on cytology specimens. Seventeen different fixation and processing platforms prior to antibody reaction were reported. A total of 59.2% of laboratories reported differences between the platforms for cytology specimens and positive controls, but most (155 of 184; 84%) did not alter antibody dilutions or antigen retrieval for cytology IHC. When asked to name 2 antibodies for which staining conditions differed between cytology and surgical samples, there were 18 responses listing 14 antibodies. A total of 30.6% of laboratories performing IHC offered HER2 testing before publication of the 2007 College of American Pathologists/American Society of Clinical Oncologists guidelines, compared with 33.6% afterward, with increased performance of testing by reference laboratories. Three laboratories validated a nonformalin HER2 platform.

CONCLUSIONS

The platforms for cytology IHC and positive controls differ for most laboratories, yet conditions are uncommonly adjusted for cytology specimens. Except for the unsuitability of air-dried smears for HER2 testing, the survey did not reveal evidence of systematic problems with any antibody or platform.

Detection of ALK-positive non-small-cell lung cancers on cytological specimens: high accuracy of immunocytochemistry with the 5A4 clone

INTRODUCTION

Lung cancer is often diagnosed by cytology, necessitating predictive molecular marker analyses on cytological specimens. The gold standard for detection of predictive anaplastic lymphoma kinase (ALK)-rearrangements is fluorescence in situ hybridization (FISH), but FISH is both expensive and often challenging to interpret. The aim of our study was to investigate the accuracy of ALK immunocytochemistry (ICC) on cytological specimens of non-small-cell lung cancers (NSCLCs).

METHODS

Forty-one cytological specimens with available ALK FISH results were retrospectively analyzed with the 5A4 monoclonal antibody (Novocastra; Leica Biosystems) on a fully automated slide stainer. The specimens were enriched for ALK FISH-positive NSCLCs (14 of 41; 34.1%). Evaluation of the ICC staining was performed blinded to the FISH results. The staining intensity and the percentage of stained cancer cells were recorded. Any ICC staining was regarded as a positive result. The ALK ICC results were compared with the FISH results. In case of a discrepancy the ICC-stained slide and the FISH signals were reviewed.

RESULTS

ICC was evaluable on 40 of 41 specimens. Fifteen of 40 NSCLCs (37.5%) were ALK ICC-positive, with staining of the majority of cancer cells (median 100%; mean 82.3%). Twelve of the ICC-positive NSCLCs (80.0%) showed an intense staining (3+). Compared with the ALK FISH results, only one NSCLC was false-negative, and one false-positive by ICC, respectively. The sensitivity, specificity, and positive and negative predictive values for ALK ICC compared with ALK FISH were 93.3%, 96.0%, 93.3%, and 96%, respectively.

CONCLUSION

ALK ICC is highly accurate for detecting ALK-rearranged NSCLCs.