Evidence-based Guidelines for the Utilization of Immunostains in Diagnostic Pathology: Pulmonary Adenocarcinoma Versus Mesothelioma

Utility of Claudin-4 versus BerEP4 and B72.3 in pleural fluids with metastatic lung adenocarcinoma

INTRODUCTION

Lung adenocarcinoma (LADC) is the most common occult primary in patients presenting with a malignant pleural effusion. Distinguishing metastatic LADC from reactive mesothelial cells (RMC) and malignant mesothelioma (MM) based on morphology alone has been a persistent diagnostic challenge in cytopathology. Claudin-4, a major functional constituent of tight junctions, has been shown to help distinguish LADC from RMC and MM in surgical specimens. Our goal was to further validate and assess the utility of Claudin-4 in comparison to BerEP4 and B72.3 in malignant effusions with a focus on metastatic LADC.

MATERIALS AND METHODS

We evaluated 58 pleural effusions (40 LADC, 10 RCM, and 8 MM). Immunohistochemistry was performed using Claudin-4, Ber-EP4, and B72.3 on cell blocks. Staining patterns, quantity of tumor cells, and intensity of staining (weak, moderate, or strong) were assessed.

RESULTS

All cases of LADC were positive for Claudin-4 with an overall sensitivity of 100% (40 of 40) and specificity of 100% (18 of 18). In addition, Claudin-4 showed the highest quantity and quality of staining with 3+ staining intensity in 73% (29 of 40) of cases, compared with 35% (14 of 40) of cases using BerEP4 and 52% (21 of 40) of cases using B72.3. The sensitivity and specificity for BerEP4 were 90% and 78%, respectively. The sensitivity and specificity for B72.3 were 87.5% and 100%, respectively.

CONCLUSIONS

In this study, Claudin-4 performed superiorly compared to BerEP4 and B72.3 in distinguishing lung adenocarcinoma from RMC or MM in pleural effusions. Our results show Claudin-4 is a useful marker for distinguishing RMC and MM from lung adenocarcinoma, with high sensitivity (100%) and specificity (100%), compatible with studies shown in the literature.

Pathology in the era of "Personalized Medicine": The need to learn how to integrate multivariate immunohistochemical and "omics" data with clinicopathologic information in a clinically relevant way"

"Personalized medicine" has been proposed as a new paradigm for patient care that, based on the integration of genomics and other "omics" data with clinical and other multidisciplinary information, promises early disease detection, improved outcomes and reduced side effects to therapies. Pathologists have become important participants in this new approach as the guardians of tissues and experts in the performance of molecular and other laboratory tests. Large amounts of new laboratory data in multiple neoplasms and other entities are being reported but there has been limited discussion about how best to evaluate the clinical significance of this information and how to integrate it into currently available diagnostic and therapeutic modalities. This article introduces a variety of epistemological problems presented by the "personalized medicine" paradigm and briefly discusses various topics that will be evaluated in further detail in future articles of this new series on Evidence-Based Pathology.

Pathology reporting of malignant pleural mesothelioma first diagnosis: A population-based approach

Accurate pathologic diagnosis and reporting in malignant pleural mesothelioma are essential for clinical care, and cancer registration. Practical guidelines for pathologists are provided in publications and textbooks but it is unclear how these recommendations are applied in routine practice. We investigated the characteristics of pathology reports, and the extent to which they meet guideline standards. We reviewed 819 pathology reports relating to a first diagnosis of malignant pleural mesothelioma. Data sources were a regional section of the Italian network of the Mesothelioma Registry (2001-2014) and a pathology archive (1990-2000). We evaluated tumor characteristics, the diagnosis field including terminology and immunohistochemistry (IHC) workup, and report completeness (the proportion of items recorded). We investigated also two IHC panels identified by the most used markers in current practical guidelines, one best suited for epithelioid mesotheliomas (combinations of at least 2 positive and at least 2 negative mesothelioma markers) and the other best suited for sarcomatoid mesotheliomas (positive mesothelioma markers plus cytokeratins). Reports (753 histology, 66 cytology, IHC-confirmed 86%) were 74% complete and always narrative. Missing data were related to clinical history (76%), tumor laterality (61%), specimen size (38%), and histological subtype (23%). The proportion of cases with IHC was higher for epithelioid (90%) than sarcomatoid mesothelioma (87%). Compliance to IHC recommendations was higher for epithelioid (59%) than sarcomatoid mesothelioma (11%). The mean number of stains was significantly higher for sarcomatoid than epithelioid mesothelioma (p<0.000; Kruskal-Wallis test). Our findings show that although guidelines are designed to improve actual reporting practices, there is ample room for improvement in their application to standardize the diagnosis of mesothelioma. Synoptic pathology reporting needs to be implemented to better utilize pathology information.

Evidence-based pathology: systematic literature reviews as the basis for guidelines and best practices

CONTEXT

Evidence-based medicine has been proposed as a new paradigm for the identification and evaluation of medical information. Best available evidence or data are identified and used as the basis for the diagnosis and treatment of individual patients. Evidence-based pathology has adapted basic evidence-based medicine concepts to the specific needs of pathology and laboratory medicine.

OBJECTIVES

To briefly review the history and basic concepts of evidence-based medicine and evidence-based pathology, describe how to perform and interpret systematic reviews, and discuss how to integrate best evidence into guidelines.

DATA SOURCES

PubMed (National Library of Medicine, Washington, DC) and Web of Science (Thompson Reuters, New York, New York) were used.

CONCLUSIONS

Evidence-based pathology provides methodology to evaluate the quality of information published in pathology journals and apply it to the diagnosis of tissue samples and other tests from individual patients. Information is gathered through the use of systematic reviews, using a method that is less biased and more comprehensive than ad hoc literature searches. Published data are classified into evidence levels to provide readers with a quick impression about the quality and probable clinical validity of available information. Best available evidence is combined with personal experience for the formulation of evidence-based, rather than opinion-based, guidelines that address specific practice needs.

Expression and diagnostic values of calretinin and CK5/6 in cholangiocarcinoma

BACKGROUND

Mesothelin, a mesothelial marker, has been found expressed in and as a potential treatment target of cholangioacarcinoma (CC). It is possible that CC may be derived from the cells sharing mesothelial markers. However, the expression of other mesothelial markers in CC is largely unknown.

METHODS

Thirty CC cases (10 extrahepatic and 20 intrahepatic) were retrieved from our institutional archive. The immunohistochemical study of Calretinin (DC8), WT1 (6F-H2), Lymphatic Endothelial Marker (D2-40), CK5/6 (D5/16 B4) and CK19 (b170) was done on formalin fixed paraffin embedded sections for 2-3 blocks of each case. We compared the expression levels between CC and normal bile duct (NBD) on the same block.

RESULTS

All of the CC and NBD are positive for CK19 (23/23) and negative for WT1 (0/23) and D2-40 (0/23), except one CC positive for D2-40(1/30, 3.3%) and one NBD positive for WT1 (1/23, 4.3%). Calretinin immunoreactivity was detected in 52.2% (12/23) of CC, but none in NBD (0/23). CK5/6 was also detectable in 73.3% (22/30) of CC and all NBD (30/30). Increased expression of calretinin and reduced expression of CK5/6 were more likely associated with CC than NBD (P < 0.001 and P = 0.002, respectively). The sequential staining pattern of positive calretinin and negative CK5/6 in calretinin negative cases has a sensitivity of 69.57% and a specificity of 100% for differentiating CC from NBD. CK5/6 expression was also more likely associated with well-differentiated CC (7/7 versus 12/20 in moderately differentiated, and 9/10 in poorly differentiated, P = 0.019) and extrahepatic CC (10/10 versus 12/20 in intrahepatic, P = 0.029), but there was no association between the calretinin expression and the CC grade or location.

CONCLUSION

Calretinin and CK5/6 immunohistochemical stains may be useful for diagnosing a CC. Their immunohistochemical results should be interpreted with caution in the cases with differential diagnoses of mesothelioma and CC. A full mesothelioma panel, including WT1 and/or D2-40, is recommended to better define a mesothelial lineage. The biology of calretinin and CK5/6 expression in CC is unclear, but might shed light on identifying therapeutic targets for CC.

Claudin-4 immunohistochemistry is highly effective in distinguishing adenocarcinoma from malignant mesothelioma in effusion cytology

BACKGROUND

Adenocarcinoma can be challenging to distinguish from malignant mesothelioma in effusions, and this distinction often requires ancillary studies and clinical correlation. Immunohistochemistry for claudin-4, a tight-junction-associated protein, has recently been shown to distinguish adenocarcinoma from malignant mesothelioma, mostly in surgical specimens. Our aim was to validate and assess the immunoreactivity profile of claudin-4 in a large series of malignant effusions.

METHODS

We evaluated 159 malignant effusions (84 adenocarcinomas and 75 malignant mesotheliomas). Claudin-4 immunohistochemistry was performed on cell-block paraffin sections and scored for staining intensity, staining pattern (cytoplasmic versus membranous), and percentage of positive tumor cells. Appropriate positive and negative controls were used throughout.

RESULTS

All cases of mesothelioma were negative for claudin-4 (0 of 64). Eighty-three of 84 cases of adenocarcinoma were positive (99%); 1 case of serous carcinoma was negative. Most adenocarcinomas showed strong and diffuse membranous staining (71 of 84; 84%); 12 cases (14%) showed membranous staining of moderate intensity. The overall sensitivity for adenocarcinoma was 99% (83 of 84).

CONCLUSIONS

Claudin-4 immunohistochemistry effectively distinguishes adenocarcinoma from malignant mesothelioma with high sensitivity and specificity in the evaluation of malignant effusions.

Patterns in Immunohistochemical Usage in Extended Core Prostate Biopsies: Comparisons Among Genitourinary Pathologists and Nongenitourinary Pathologists

Context.—Immunohistochemical (IHC) stains have known utility in prostate biopsies and are widely used to augment routine staining in difficult cases. Patterns in IHC utilization and differences based on pathologist training and experience is understudied in the peer-reviewed literature.

Objectives.—To compare the rates of IHC usage between specialized (genitourinary; [GU]) and nonspecialized (non-GU) pathologists in extended core prostate biopsies (ECPBs) and the effects of diagnosis; and in cancer cases Gleason grade, disease extent, and perineural invasion on the rate.

Design.—Consecutive ECPBs from 2009–2011 were identified and billing data were used to determine the number of biopsies and IHC stains per case. Diagnoses were mapped and in cancer cases, Gleason grade, extent of disease, and perineural invasion were recorded. Pathologists were classified as GU or non-GU on the basis of training and experience.

Results.—A total of 618 ECPBs were included in the study. Genitourinary pathologists ordered significantly fewer IHC tests per case and per biopsy than non-GU pathologists. The rate of ordering was most disparate for biopsies of cancerous and benign lesions. For biopsies of cancerous lesions, high-grade cancer, bilateral disease, and perineural invasion decreased the rate of ordering in both groups. In cancer cases, GU pathologists ordered significantly fewer stain tests for highest Gleason grade of 3 + 3 = 6, for patients with focal disease and for patients with multiple positive bilateral cores. The effect of the various predictors on IHC ordering rates was similar in both groups.

Conclusions.—Genitourinary pathologists ordered significantly fewer IHC stain tests than non-GU pathologists in ECPBs. Guidelines to define when IHC workup is necessary and not necessary may be helpful to guide workups.

Immunohistochemistry and Molecular Diagnostics of Pleural Malignant Mesothelioma

Context.—The pathologic approach to pleural-based lesions is stepwise and uses morphologic assessment, correlated with clinical and imaging data supplemented by immunohistochemistry (IHC), and more recently, molecular tests, as an aid for 2 main diagnostic problems: malignant mesothelioma (MM) versus other malignant tumors and malignant versus reactive mesothelial proliferations.

Objective.—To present the current knowledge regarding IHC and molecular tests with respect to MM diagnosis, and in particular, the differentiation of the epithelioid type of MM from carcinoma metastatic to the pleural cavity.

Data Sources.—A review of immunohistochemical features of 286 consecutive MMs from 459 cases of pleural pathology, diagnosed during routine practice from 2003 to 2009. A survey of biomedical journal literature from MedLine/PubMed (US National Library of Medicine) focused on MM and associated tissue-based diagnostic IHC markers and molecular tests.

Conclusions.—The search for a single diagnostic marker of MM has so far been discouraging, given the biologic and phenotypic tumor heterogeneity of MM. The use of antibody panels has gained unanimous acceptance especially in the differential diagnosis between MM and metastatic carcinoma, whereas the usefulness of IHC is more limited when dealing with spindle cell malignancies or distinguishing malignant from reactive mesothelium. A great degree of interlaboratory variability in antibody combinations and clone selection within diagnostic panels still exists. Current investigations aim at selecting the most suitable and cost-effective combination of antibodies by using novel statistical approaches for assessing diagnostic performance beyond the traditional measures of sensitivity and specificity.

Evidence-Based Principles in Pathology: Existing Problem Areas and the Development of “Quality” Practice Patterns

Context.—Contrary to the intuitive impressions of many pathologists, several areas exist in laboratory medicine where evidence-based medicine (EBM) principles are not applied. These include aspects of both anatomic and clinical pathology. Some non-EBM practices are perpetuated by clinical “consumers” of laboratory services because of inadequate education, habit, or overreliance on empirical factors. Other faulty procedures are driven by pathologists themselves.

Objectives.—To consider (1) several selected problem areas representing non-EBM practices in laboratory medicine; such examples include ideas and techniques that concern metastatic malignancies, “targeted” oncologic therapy, general laboratory testing and data utilization, evaluation of selected coagulation defects, administration of blood products, and analysis of hepatic iron-overload syndromes; and (2) EBM principles as methods for remediation of deficiencies in hospital pathology, and implements for the construction of “quality” practices in our specialty.

Data Sources.—Current English literature relating to evidence-based principles in pathology and laboratory medicine, as well as the authors' experience.

Conclusions.—Evidence-based medicine holds the promise of optimizing laboratory services to produce “quality” practices in pathology. It will also be a key to restraining the overall cost of health care.

Re-evaluation of histological diagnoses of malignant mesothelioma by immunohistochemistry

Background

In order to provide reliable tissue material for malignant mesothelioma (MM) studies, we re-evaluated biopsies and autopsy material from 61 patients with a diagnosis of MM from the period of 1980-2002.

Methods

Basic positive (Calretinin, EMA, Podoplanin, Mesothelin) and negative (CEA, Ber-Ep4) immunohistochemical (IHC) marker reactions were determined. If needed, more markers were used. Histological diagnoses were made by three pathologists. Survival data were calculated.

Results

49 cases (80%) were considered being MM by a high degree of likelihood, five more cases possible MM. Of the remaining seven cases, three were diagnosed as adenocarcinoma, three as pleomorphic lung carcinoma, in one peritoneal case a clear entity diagnosis could not be given. One of the possible MM cases and two of the lung carcinoma cases had this already as primary diagnoses, but were registered as MM.

With a sensitivity of 100%, Calretinin and CEA were the most reliable single markers. The amount of MM cells with positive immunoreactivity (IR) for Podoplanin and Mesothelin showed most reliable inverse relation to the degree of atypia.

In the confirmed MM cases, there had been applied either no IHC or between one and 18 markers.

The cases not confirmed by us had either lacked IHC (n = 1), non-specific markers were used (n = 4), IR was different (n = 1), or specific markers had not shown positive IR in the right part of the tumour cells (n = 3).

46 of the 49 confirmed and three of the not confirmed cases had been diagnosed by us as most likely MM before IHC was carried out.

Conclusions

In order to use archival tissue material with an earlier MM diagnosis for studies, histopathological re-evaluation is important. In possible sarcomatous MM cases without any positive IR for positive MM markers, radiology and clinical picture are essential parts of diagnostics. IHC based on a panel of two positive and two negative MM markers has to be adapted to the differential diagnostic needs in each single case. New diagnostic tools and techniques are desirable for cases where IHC and other established methods cannot provide a clear entity diagnosis, and in order to improve MM treatment.

Diagnosis of Metastatic Neoplasms: A Clinicopathologic and Morphologic Approach

Context.—The diagnosis of the site of origin of metastatic neoplasms often poses a challenge to practicing pathologists. A variety of immunohistochemical and molecular tests have been proposed for the identification of tumor site of origin, but these methods are no substitute for careful attention to the pathologic features of tumors and their correlation with imaging findings and other clinical data. The current trend in anatomic pathology is to overly rely on immunohistochemical and molecular tests to identify the site of origin of metastatic neoplasms, but this “shotgun approach” is often costly and can result in contradictory and even erroneous conclusions about the site of origin of a metastatic neoplasm.

Objective.—To describe the use of a systematic approach to the evaluation of metastatic neoplasms.

Data Sources.—Literature review and personal experience.

Conclusions.—A systematic approach can frequently help to narrow down differential diagnoses for a patient to a few likely tumor sites of origin that can be confirmed or excluded with the use of selected immunohistochemistry and/or molecular tests. This approach involves the qualitative evaluation of the “pretest and posttest probabilities” of various diagnoses before the immunohistochemical and molecular tests are ordered. Pretest probabilities are qualitatively estimated for each individual by taking into consideration the patient's age, sex, clinical history, imaging findings, and location of the metastases. This estimate is further narrowed by qualitatively evaluating, through careful observation of a variety of gross pathology and histopathologic features, the posttest probabilities of the most likely tumor sites of origin. Multiple examples of the use of this systematic approach for the evaluation of metastatic lesions are discussed.

Differentiation of lung adenocarcinoma, pleural mesothelioma, and nonmalignant pulmonary tissues using DNA methylation profiles

Pathologic differentiation of tissue of origin in tumors found in the lung can be challenging, with differentiation of mesothelioma and lung adenocarcinoma emblematic of this problem. Indeed, proper classification is essential for determination of treatment regimen for these diseases, making accurate and early diagnosis critical. Here, we investigate the potential of epigenetic profiles of lung adenocarcinoma, mesothelioma, and nonmalignant pulmonary tissues (n = 285) as differentiation markers in an analysis of DNA methylation at 1413 autosomal CpG loci associated with 773 cancer-related genes. Using an unsupervised recursively partitioned mixture modeling technique for all samples, the derived methylation profile classes were significantly associated with sample type (P < 0.0001). In a similar analysis restricted to tumors, methylation profile classes significantly predicted tumor type (P < 0.0001). Random forests classification of CpG methylation of tumors--which splits the data into training and test sets--accurately differentiated mesothelioma from lung adenocarcinoma over 99% of the time (P < 0.0001). In a locus-by-locus comparison of CpG methylation between tumor types, 1266 CpG loci had significantly different methylation between tumors following correction for multiple comparisons (Q < 0.05); 61% had higher methylation in adenocarcinoma. Using the CpG loci with significant differential methylation in a pathway analysis revealed significant enrichment of methylated gene-loci in Cell Cycle Regulation, DNA Damage Response, PTEN Signaling, and Apoptosis Signaling pathways in lung adenocarcinoma when compared with mesothelioma. Methylation profile-based differentiation of lung adenocarcinoma and mesothelioma is highly accurate, informs on the distinct etiologies of these diseases, and holds promise for clinical application.

MOC-31 exhibits superior reactivity compared with Ber-EP4 in invasive lobular and ductal carcinoma of the breast: a tissue microarray study

Distinguishing between reactive mesothelial proliferations and adenocarcinoma is often very difficult. Ancillary studies, in particular immunohistochemistry, are often critical in detecting malignant epithelial cells, especially in serous effusion specimens. MOC-31 and Ber-EP4 are antibodies which target the epithelial cell adhesion molecule (Ep-CAM, TACSTD1) expressed in epithelial cells, and both are useful in distinguishing metastatic adenocarcinoma from reactive mesothelial cells. However, the reactivity of MOC-31 and Ber-EP4 with breast carcinoma, one of the more common carcinomas involving serous effusions, has not been extensively studied. We analyzed the immunohistochemical expression of MOC-31 and Ber-EP4 using tissue microarrays containing invasive ductal carcinoma (191 cases), invasive lobular carcinoma (44 cases), and 102 other carcinoma types comprising primary carcinomas of lung, gynecologic tract, pancreas, colon, gastric, esophageal, prostate, head and neck, hepatic, and renal origin. For MOC-31, 184 of 191 (96%) invasive ductal carcinomas and 39 of 44 (89%) invasive lobular carcinomas exhibited diffuse positive staining. In contrast, for Ber-EP4, 121 of 183 (66%) invasive ductal carcinomas and 11 of 40 (27.5%) invasive lobular carcinomas exhibited diffuse positive staining. With the exception of 1 case of esophageal adenocarcinoma, all other adenocarcinomas (86 of 87 cases) exhibited diffuse staining with both Ber-EP4 and MOC-31. MOC-31 and Ber-EP4 exhibited identical staining with all other carcinoma types. Our findings indicate that MOC-31 is superior to Ber-EP4 in detecting both invasive lobular and ductal carcinoma of the breast.

Challenges in the interpretation of peritoneal cytologic specimens

CONTEXT

The presence of malignant cells in peritoneal washings leads to classification as International Federation of Gynecology and Obstetrics stage IC or higher in ovarian carcinomas and at least International Federation of Gynecology and Obstetrics stage IIIA in endometrial carcinomas. Unfortunately, the morphologic examination of cytologic specimens has not proven to be a sensitive or specific diagnostic tool. Malignant cells might be few in number and might be unrecognized among a large population of mesothelial cells and/or macrophages, or reactive mesothelial cells might be misinterpreted as neoplastic cells leading to unnecessary chemotherapy.

OBJECTIVE

To evaluate the main pitfalls in the evaluation of peritoneal washings in patients with gynecologic malignancies and analyze the ancillary studies that might be helpful to achieve the correct diagnosis with an emphasis on immunocytochemistry.

DATA SOURCES

A comprehensive review of the literature was performed.

CONCLUSIONS

Peritoneal effusions may represent major challenges to the pathologist and can have important clinical implications. Immunostains for epithelial markers such as B72.3, MOC-31, and Ber-EP4 represent the best available markers to identify epithelial cells. Caution is advised to not overdiagnose endometriosis or endosalpingiosis as adenocarcinoma.

Application of immunohistochemistry to the diagnosis of malignant mesothelioma

CONTEXT

The diagnosis of malignant mesothelioma (MM) is rendered with the aid of immunohistochemistry to demonstrate the presence of "mesothelial," "epithelial," or "sarcomatous" differentiation. Antibody panels that have been proposed for the distinction between MM and other neoplasms usually include 2 or more epithelial markers used to exclude the diagnosis of a carcinoma, such as monoclonal and polyclonal carcinoembryonic antigen, Ber-EP4, B72.3, CD15, MOC-31, thyroid transcription factor 1, BG8, and others, and 2 or more mesothelial markers used to confirm the diagnosis of MM, such as cytokeratin 5/6, calretinin, HBME-1, thrombomodulin, WT-1, mesothelin, D2-40, and podoplanin. In general, most antibody panels provide excellent sensitivity and specificity for the differential diagnosis between MM epithelial variant and adenocarcinoma, particularly of lung origin. However, the accuracy of these markers is lower for the diagnosis of sarcomatous MM and for the differential diagnosis between MM and squamous cell carcinoma and carcinomas of renal, ovarian, and other origin.

OBJECTIVE

To identify optimal antibody panels for the diagnosis of MM.

DATA SOURCES

Literature review to determine how many and which mesothelial and epithelial markers need to be included in differential diagnosis antibody panels.

CONCLUSIONS

Various antibody panels have been recommended for the diagnosis of MM, with no overall consensus about how many and which markers should be used. A recent study with Bayesian statistics has demonstrated that the use of many markers does not provide higher diagnostic accuracy than the use of selected single antibodies or various combinations of only 2 markers. There is a need for the development of evidence-based or consensus-based guidelines for the diagnosis of MM in different differential diagnosis situations.