Guidelines for cytopathologic diagnosis of epithelioid and mixed type malignant mesothelioma. Complementary statement from the International Mesothelioma Interest Group, also endorsed by the International Academy of Cytology and the Papanicolaou Society of Cytopathology

Second opinion for pulmonary and pleural cytology is valuable for patient care

INTRODUCTION

Thoracic cytology can be challenging due to limited procured material or overlapping morphology between benign and malignant entities. In such cases, expert consultation might be sought. This study aimed to characterize all pulmonary and pleural cytology consult cases submitted to our practice and provide recommendations on approaching difficult cases.

MATERIALS AND METHODS

All thoracic (pulmonary and pleural) cytology cases submitted for expert consultation to the University of Michigan (MLabs) from 2013 to mid-2022 were reviewed. Cases where cytology was only part of a hematopathology or surgical pathology consult were excluded. Patient demographics, specimen location, procedure performed, referring diagnosis, and our diagnoses were recorded for each case. Diagnoses were categorized according to the Papanicolaou Society of Cytopathology recommendations for pulmonary and effusion cytology. Discordant diagnoses were stratified as major or minor. Data was analyzed using chi-square analysis and logistic models.

RESULTS

We received 784 thoracic cytology consult cases, including 530 exfoliative samples and 307 fine-needle aspirations. The most common anatomic locations sampled were the bronchial wall (n = 194, 23%), lung nodule (n = 322, 38%), and pleura (n = 296, 35%). 413 cases had a diagnostic discrepancy (48.3%), with 274 (66%) minor and 139 (34%) major discrepancies. By location, pleural effusion specimens had the highest probability of a discrepant diagnosis (P = 0.003). By specimen type, fine-needle aspiration samples were significantly more likely to have a discrepant diagnosis (P = 0.06).

CONCLUSION

Nearly half of the thoracic cytology cases submitted for expert second opinion had diagnostic discrepancies. Consequently, consulting a tertiary medical care center with cytopathology expertise for challenging thoracic cytology diagnoses is beneficial.

Role of Ancillary Techniques in Reporting Serous Fluid Cytology - "Redefining Categories, Refining Diagnosis"

Background

The "International System of Reporting Serous Fluid Cytology (TIS)" together with cytomorphology promotes the use of ancillary techniques to resolve difficulties in reporting serous fluid cytology.

Objective

To classify serous effusion fluid samples received at our department in line with "TIS", indicating the risk of malignancy (ROM), and directing appropriate usage of ancillary testing.

Materials and Methods

Prospective study carried out from October 2021 to September 2022. The study included all pleural, ascitic, and pericardial fluid samples, reported according to 'TIS'. Flow cytometry and immunocytochemistry were ancillary methods utilized to assist in reporting. Cases with available history and convincing correlations didn't require further assessment.

Results

A total of 1200 serous effusion samples were evaluated including 604 pleural, 591 ascitic, and 5 pericardial fluid samples. After categorization, there were 23 samples in non-diagnostic (ND, 1.9%), 575 in negative for malignancy (NFM, 47.91%), 44 in atypia of undetermined significance (AUS, 3.66%), 64 in suspicious for malignancy (SFM, 5.33%), and 494 in malignant category (MAL, 41.16%). Ancillary studies were beneficial in the recategorization of 26% (11/44) AUS cases, 29.6% (19/64) SFM cases, and it helped refine tumor characteristics in 35.42% (175/494) cases categorized as malignant. Final ROM calculated for each category: ND 25%, NFM 18.6%, AUS 66.6%, SFM 88%, and MAL 100%.

Conclusion

Serous fluid is an easily obtainable sample that can provide opportunities for ancillary testing with clinical implications. In AUS and suspicious category although, diagnostic yield is increased however, a larger number of cases are required to obtain definite results.

Investigation of MTAP and BAP1 staining loss and P16/CDKN2A deletion in pleural cytology specimens and its role in the diagnosis of mesothelioma

BACKGROUND

Mesothelioma is a malignant neoplasm with a poor survival rate. We aimed to investigate the importance of BAP1, MTAP (IHC), and p16/CDKN2A homozygous deletion (FISH) in cytologic material obtained from pleural effusion sampling, which is a less invasive procedure in the diagnosis of mesothelioma.

METHODS

Our study discussed pleural cytology samples of cases with histopathologically proven mesothelioma diagnoses between 2017 and 2022. As the control group, materials that had pleural effusion sampling for other reasons and reactive mesothelial hyperplasia were included in the study. Cell blocks prepared from these materials were subjected to fluorescent in situ hybridization for p16/CDKN2A homozygous deletion and immunohistochemistry for BAP1 and MTAP.

RESULTS

The specificity of the P16/CDKN2A homozygous deletion in diagnosing mesothelioma is 100%. Its sensitivity is 68.75%. The specificity of BAP1 immunohistochemical nuclear expression loss is 95%, while the sensitivity is 60%. Loss of nuclear expression of MTAP alone has the lowest specificity and sensitivity, with a specificity of 86% and a sensitivity of 43%. The highest sensitivity is reached when BAP1 loss and p16/CDKN2A homozygous deletion are evaluated together, increasing to 81%. The specificity is 95%.

CONCLUSION

It has been determined that any marker alone cannot be used for a definitive mesothelioma diagnosis in pleural effusion cytological specimens; however, sensitivity increases in some combinations. The combination of BAP1 immunohistochemistry and p16/CDKN2A homozygous deletion detected by FISH, which has a higher specificity and sensitivity, can be routinely used in the diagnosis of mesothelioma under the guidance of clinical and radiologic information.

Malignant pleural disease: a pragmatic guide to diagnosis

PURPOSE OF REVIEW

The diagnosis of malignant pleural disease is important in the care of patients with cancer. However, a one-size-fits-all approach to diagnosis may lead to delays in care as the sensitivity of each biopsy modality varies and can be dependent on the tumor type. We review current literature on pleural biopsy techniques and propose a diagnostic algorithm for suspected malignant pleural disease.

RECENT FINDINGS

Recent literature has shown that the sensitivity of pleural fluid cytology varies based on tumor type resulting in a limited value of repeated thoracenteses in many cases. Furthermore, the ability to test for molecular biomarkers on pleural fluid samples has contributed to the recommendations to send large volumes of pleural fluid for analysis. Studies have also supported the consideration of medical thoracoscopy earlier in the diagnostic work-up of malignant pleural disease.

SUMMARY

The decision to repeat a diagnostic thoracentesis when suspecting malignant pleural effusions should take into account the primary tumor type. Open pleural biopsy with medical thoracoscopy has been shown to be a relatively safe diagnostic modality with high sensitivity and should be considered in patients with a nondiagnostic thoracentesis.

Evaluation of DNA/RNA quality from cell block of malignant mesothelioma and lung adenocarcinoma

Malignant mesothelioma (MM) is a rare and highly lethal tumor that arises from mesothelial tissue on the surface of the chest and abdominal cavity. Cytological examination of body fluids, including pleural fluid and ascites, is essential for the differentiation of malignant mesothelioma from other carcinomas, such as lung and gastrointestinal carcinomas and metastatic tumors. To evaluate the effectiveness of cell block preparation procedures, which are used for immunocytochemical staining and genetic panel analysis of tumor-specific gene mutations, we used various fixatives. We also evaluated the effects of immunostaining, and the quality of nucleic acids for genetic analysis.

METHODS

Cell blocks were prepared using the malignant mesothelioma cell lines MESO4 and H226 and non-small cell lung carcinoma cell line HCC78. The cells were fixed using 10% neutral buffered formalin and four different fixatives for liquid cytology. Fixed cells were formed into cell clusters using sodium alginate or centrifugation, and paraffin-embedded cell blocks were prepared.

RESULTS

Cell blocks were morphologically evaluated by hematoxylin and eosin and immunocytological staining, and the nucleic acid quality was evaluated by DNA/RNA extraction, qPCR, and next-generation sequence analysis. D2-40 and WT1 staining differed depending on the fixation solution and the cell cluster formation method; however, the degree of nucleic acid degradation was not impaired by any method.

CONCLUSION

Although the morphological evaluation of cytology specimens is affected by the method of cell block preparation, it is still useful for nucleic acid extraction and gene panel analysis, as long as there are sufficient amounts of tumor cells.

Evidence-based diagnostic performance of novel biomarkers for the diagnosis of malignant mesothelioma in effusion cytology

Cytology effusions are often the only material available for diagnosing malignant pleural mesothelioma (MPM). However, the cytomorphological features alone are not always diagnostic, and cytology samples preclude an assessment for pleural tissue invasion. Accordingly, immunohistochemical, soluble, and molecular biomarkers have been developed. The aim of this study is to provide quantitative evidence regarding the diagnostic performance of novel biomarkers. To that end, a systematic literature review was performed of articles dealing with a loss of BRCA1-associated protein 1 (BAP1), methylthioadenosine (MTAP), 5-hydroxymethylcitosine (5-hmC), glucose transporter 1 (GLUT1), insulin like-growth factor II messenger RNA-binding protein 3 (IMP3), enhanced zeste homologue 2 (EZH2) staining, cyclin-dependent kinase inhibitor 2A (CDKN2A) homozygous deletion (HD) testing, soluble mesothelin, and microRNA quantification in cytological samples for the diagnosis of MPM versus reactive atypical mesothelial cells. Sensitivity and specificity were extracted, and a meta-analysis was performed. The quality of the studies was assessed with Quality Assessment of Diagnostic Accuracy Studies 2, and the quality of the evidence was evaluated with the Grading of Recommendations Assessment, Development, and Evaluation approach. Seventy-one studies were included. BAP1 loss showed a sensitivity of 0.65 (confidence interval [CI], 0.59-0.71) and a specificity of 0.99 (CI, 0.93-1.00). MTAP loss and p16 HD showed 100% specificity with sensitivities of 0.47 (CI, 0.38-0.57) and 0.62 (CI, 0.53-0.71), respectively. BAP1 loss and CDKN2A HD combined showed maximal specificity and a sensitivity of 0.83 (CI, 0.78-0.89). GLUT1 and IMP3 showed sensitivities of 0.82 (CI, 0.70-0.90) and 0.65 (CI, 0.41-0.90), respectively, with comparable specificity. Mesothelin showed a sensitivity of 0.73 (CI, 0.68-0.77) and a specificity of 0.90 (CI, 0.84-0.93). In conclusion, some of the recently emerging biomarkers are close to 1.00 specificity. Their moderate sensitivity on their own, however, can be significantly improved by the use of 2 biomarkers, such as a combination of BAP1 and CDKN2A with fluorescence in situ hybridization or a combination of BAP1 and MTAP immunohistochemistry.

Role of Cytology in the Current Guidelines for Malignant Mesothelioma: Largest Study from India

INTRODUCTION

Cytology provides crucial window for early diagnosis of malignant mesothelioma (MM) since it is often the first and easily available material for evaluation, resulting in early treatment. Still, its role is overlooked in the current treatment guidelines. The aim of this study is to determine the sensitivity of cytomorphology and role of subsequent ancillary techniques in diagnosing MM.

METHODS

This is a 5-year retrospective analysis of MM in the tertiary oncology center to determine sensitivity of cytomorphology and subsequent role of immunohistochemistry (IHC) in final diagnosis of MM according to the guidelines for cytopathologic diagnosis of epithelioid and mixed-type malignant mesothelioma (GCDMM) laid by International Mesothelioma Interest Group. Cytomorphology and immunocytochemistry from effusions and fine needle aspirations were analyzed.

RESULTS

Sixty-two of 128 cases of MM had cytology and cytomorphological criteria described in GCDMM were fulfilled in 61.3% cases. Architectural atypia was useful in identifying cases with low cytological atypia. Overall sensitivity of cytomorphology was 73.01%. Sensitivity of effusion cytology was 77.8%. Subsequent IHC on cell blocks revealed the sensitivity as 100% for mesothelin, calretinin, and cytokeratin 5/6; 87.5% for thrombomodulin; and 50% for WT1, while CEA and TTF1 showed 100% specificity. Treatment was given based on final diagnosis of MM given after IHC on cytology material in only 25.8% cases. However, it was possible in additional 35.5% cases. Mean survival was 10 months when diagnosed by cytology, compared to 7 months by histology.

CONCLUSIONS

Rather than ignoring the role of cytology in the diagnosis and treatment guidelines for MM, it is important to understand its strengths and limitations. Standardized guidelines in future can play an important role in more streamlined communication between cytopathologist and clinician.

Homozygous deletion of CDKN2A in malignant mesothelioma: Diagnostic utility, patient characteristics and survival in a UK mesothelioma centre

BACKGROUND

Detection of homozygous deletion of the p16 gene (CDKN2A) by fluorescence in situ hybridization (FISH) has been investigated as an ancillary technique in the diagnosis of malignant mesothelioma.

METHOD

This retrospective study reviewed the results of all p16 FISH tests performed at a regional mesothelioma centre from February 2012 to November 2019 in cases of possible mesothelioma to examine the diagnostic utility of this test as well as patients characteristics and survival in p16 FISH positive mesothelioma versus p16 FISH negative mesothelioma.

RESULTS

P16 FISH testing was requested in 216 pathological samples in the study period. The test failure rate was 4% (10/216). Median time from request to result was 10 days (IQR 7-13, range 1-30). The sensitivity, specificity, NPV and PPV were 60 %, 100 %, 39 % and 100 % respectively. There were no false positive results and this genetic aberration was only detected in cases of mesothelioma. The prevalence of p16 FISH positive mesothelioma was higher in cytological specimens compared to histological specimens (75 % vs 58 %, p = 0.03) and lower in women compared to men (33 % vs 66 %, p = 0.003). P16 FISH positive mesothelioma was associated with significantly worse survival (median overall survival 285 vs 339 days, p = 0.0018). This remained significant after adjusting for confounding variables (OR 4.4, 95 %CI 1.84-11.14, p = 0.001).

CONCLUSIONS

In this study, 60 % of mesotheliomas harbour a homozygous deletion of CDKN2A and can be accurately, reliably and efficiently identified by p16 FISH testing. This test can be embedded within routine practice in mesothelioma pathways to enhance diagnostic accuracy.

The Use of Immunohistochemistry, Fluorescence in situ Hybridization, and Emerging Epigenetic Markers in the Diagnosis of Malignant Pleural Mesothelioma (MPM): A Review

Malignant pleural mesothelioma (MPM) is an aggressive asbestos related disease that is generally considered to be difficult to diagnose, stage and treat. The diagnostic process is continuing to evolve and requires highly skilled pathology input, and generally an extensive list of biomarkers for definitive diagnosis. Diagnosis of MPM requires histological evidence of invasion by malignant mesothelial cells often confirmed by various immunohistochemical biomarkers in order to separate it from pleural metastatic carcinoma. Often when invasion of neoplastic mesothelial cells into adjacent tissue is not apparent, further immunohistochemical testing - namely BAP1 and MTAP, as well as FISH testing for loss of p16 (CDKN2A) are used to separate reactive mesothelial proliferation due to benign processes, from MPM. Various combinations of these markers, such as BAP1 and/or MTAP immunohistochemistry alongside FISH testing for loss of p16, have shown excellent sensitivity and specificity in the diagnosis of MPM. Additionally, over the recent years, research into epigenetic marker use in the diagnosis of MPM has gained momentum. Although still in their research stages, various markers in DNA methylation, long non-coding RNA, micro RNA, circular RNA, and histone modifications have all been found to support diagnosis of MPM with generally good sensitivity and specificity. Many of these studies are however, limited by small sample sizes or other study limitations and further research into the area would be beneficial. Epigenetic markers show promise for use in the future to facilitate the diagnosis of MPM.

Malignant mesothelioma in situ: diagnostic and clinical considerations

In situ stages of malignancy have been characterised in various neoplasms. Mesothelioma in situ (MIS) has been a controversial diagnosis, lacking clear diagnostic criteria and understanding as to whether it is truly a premalignant lesion in the progression of malignant mesothelioma (MM). Originally understood as a concept and defined as atypical mesothelial proliferation in the presence of invasion, it has now been suggested that loss of nuclear labelling for BRCA1-associated protein-1 (BAP1) in flat, non-invasive mesothelial lesions can define MIS. This study aimed to characterise BAP1 expression in a cohort of 19 patients diagnosed with MIS (either pure MIS, n=3, or MIS-predominant invasive MM, n=16) and to compare survival between MIS, MIS-predominant MM and MM (n=114) in order to gain insight into the characteristics of MIS. We defined pure MIS as any architectural pattern of surface mesothelial cells with loss of BAP1 in the absence of invasion, but in specimens with superficial stromal invasion we also accepted the original definition of cytologically and architecturally atypical mesothelial proliferation, in the absence of inflammatory features, with or without loss of BAP1. We observed that MIS associated with minimal invasion was associated with significantly improved survival compared to MM (8 months vs 22 months). This suggests that MIS is indeed a precursor to MM and that these cases represent earlier stage disease. Loss of BAP1 was present in 60% of mesotheliomas with invasion, so not all early cases can be detected by BAP1 loss, but our study provides evidence that BAP1 loss may be an early molecular alteration in MM pathogenesis in patients that have loss of BAP1. We confirm that BAP1 loss can be useful for diagnosis of pure MIS in surgical specimens, permitting earlier diagnosis. However, identification of a predominant MIS component with minimal invasion has prognostic and conceptual implications. Whilst no approved therapy is available for MIS, close follow up of patients with BAP1 mutation in mesothelial cells and/or diagnosis of MIS is required to monitor for disease progression and potentially investigate earlier treatment interventions.

Multiplex Soluble Biomarker Analysis from Pleural Effusion

Malignant pleural mesothelioma (MPM) is a highly aggressive and therapy resistant pleural malignancy that is caused by asbestos exposure. MPM is associated with poor prognosis and a short patient survival. The survival time is strongly influenced by the subtype of the tumor. Dyspnea and accumulation of pleural effusion in the pleural cavity are common symptoms of MPM. The diagnostic distinction from other malignancies and reactive conditions is done using histopathology or cytopathology, always supported by immunohistochemistry, and sometimes also by analyses of soluble biomarkers in effusion supernatant. We evaluated the soluble angiogenesis related molecules as possible prognostic and diagnostic biomarkers for MPM by Luminex multiplex assay. Pleural effusion from 42 patients with malignant pleural mesothelioma (MPM), 36 patients with adenocarcinoma (AD) and 40 benign (BE) effusions were analyzed for 10 different analytes that, in previous studies, were associated with angiogenesis, consisting of Angiopoietin-1, HGF, MMP-7, Osteopontin, TIMP-1, Galectin, Mesothelin, NRG1-b1, Syndecan-1 (SDC-1) and VEGF by a Human Premixed Multi-Analyte Luminex kit. We found that shed SDC-1 and MMP-7 levels were significantly lower, whereas Mesothelin and Galectin-1 levels were significantly higher in malignant mesothelioma effusions, compared to adenocarcinoma. Galectin-1, HGF, Mesothelin, MMP-7, Osteopontin, shed SDC-1, NRG1-β1, VEGF and TIMP-1 were significantly higher in malignant pleural mesothelioma effusions compared to benign samples. Moreover, there is a negative correlation between Mesothelin and shed SDC-1 and positive correlation between VEGF, Angiopoietin-1 and shed SDC-1 level in the pleural effusion from malignant cases. Shed SDC-1 and VEGF have a prognostic value in malignant mesothelioma patients. Collectively, our data suggest that MMP-7, shed SDC-1, Mesothelin and Galectin-1 can be diagnostic and VEGF and SDC-1 prognostic markers in MPM patients. Additionally, Galectin-1, HGF, Mesothelin, MMP-7, Osteopontin, shed SDC-1 and TIMP-1 can be diagnostic for malignant cases.

Differential Diagnosis of Malignant Pleural Mesothelioma on Cytology: A Gene Expression Panel versus BRCA1-Associated Protein 1 and p16 Tests

Pleural effusions are among the first clinical manifestations of malignant pleural mesothelioma (MPM) and often constitute the only available material for diagnosis. Although an MPM diagnosis can be reliable on cytology, the reported sensitivity is low (30% to 75%). Particularly, it can be hard to discriminate epithelioid MPM, the most common histotype, from reactive mesothelial hyperplasia (MH). Currently, BRCA1-associated protein 1 (BAP1) and CDKN2A (p16), evaluated by immunohistochemistry and fluorescent in situ hybridization, respectively, are the most valuable markers to discriminate MPM and MH. Both markers have a high specificity, but their sensitivity is not always satisfying, even when used together. We have recently developed a 117-gene expression panel, based on Nanostring technology, able to differentiate epithelioid MPM from MH pleural tissues better than BAP1 and p16. Herein, we evaluated the efficacy of the same panel on an independent retrospective cohort of 23 MPM and 11 MH pleural effusions (cell blocks and smears). The overall sensitivity and specificity of the panel were equal to 0.9565 and 1, respectively. Moreover, the panel performance was compared with BAP1 and p16 on 25 cell blocks. Sensitivity levels of gene panel, BAP1 alone, p16 alone, and BAP1 plus p16 were 1, 0.5882, 0.4706, and 0.7647, respectively. Specificity was always 1. Although further validation is needed, this gene panel could really facilitate patients' management, allowing a definitive MPM diagnosis directly on pleural effusions.

Diagnostic value of GLUT-1 in distinguishing malignant mesothelioma from reactive mesothelial cells: a meta-analysis

Background: Previous studies have demonstrated the diagnostic value of glucose transporter 1 (GLUT-1) to distinguish malignant mesothelioma (MM) from reactive mesothelial cells (RMC), but the results are inconsistent. The purpose of this meta-analysis is to investigate the diagnostic accuracy of GLUT-1 in distinguishing MM from RMC.Methods: A systematical search was conducted until May 2019 in PubMed, Medline, Embase and the Cochrane Library. The revised tool for the quality assessment of diagnostic accuracy studies (QUADAS-2) was used to assess the quality of the eligible studies. The Stata15 and Review Manager5.3 software programmes were used to perform the meta-analysis.Results: A total of 24 studies, including 969 MM patients and 1080 RMC individuals were explored in the meta-analysis. The summary assessments revealed that the pooled sensitivity was 0.73 (95% CI, 0.62-0.81) and the pooled specificity was 0.95 (95% CI, 0.91-0.98). The area under the summary ROC curve (AUC) was 0.93 (95% CI: 0.91-0.95).Conclusions: GLUT-1 is highly accurate to distinguish MM from RMC.

A gene-expression-based test can outperform bap1 and p16 analyses in the differential diagnosis of pleural mesothelial proliferations

The demonstration of tissue invasion by histology is an essential criterion for the differential diagnosis of benign and malignant mesothelial proliferations. When tissue invasion cannot be identified, the use of ancillary tests is sometimes necessary. Among investigated markers, the loss of BRCA1 associated protein 1 (BAP1) protein expression and the homozygous deletion of p16 have shown 100% specificity in separating benign and malignant mesothelial lesions. However, beyond the excellent specificity of these two markers, their low sensitivity limits their clinical utility. In this context, a previous study developed and tested a novel tool for use in the differential diagnosis of malignant pleural mesothelioma (MPM) using the NanoString System and a classification algorithm. In the current study, the performance of gene classifiers were compared using BAP1 and p16 testing. p16 FISH and BAP1 immunohistochemistry were performed on the same series of 34 epithelioid MPM and 20 benign pleural lesions, which were previously analyzed by the system. The diagnostic performance of p16, BAP1 and our classification models were compared using ROC analysis. It was observed that BAP1 loss and p16 deletion were highly specific for MPM, since they were not detected in benign lesions. However, their AUC values were not completely satisfying (BAP1: 0.8235; p16: 0.7647) particularly due to their low sensitivities. As expected, combining BAP1 and p16 tests increased the diagnostic sensitivity, thus improving the AUC (0.8824). In the same series of cases, our MPM tool outperformed BAP1 and p16 tests using the 22 and 40-gene classification models (AUC 22-gene model: 0.9996; AUC 40-gene model: 0.9990). In conclusion, the present gene-expression-based classification exhibited great potential and further validation is required to support these findings in a prospective fashion, in order to provide a solid alternative for pleural proliferation diagnosis.

MicroRNA Signatures in Malignant Pleural Mesothelioma Effusions

Malignant pleural mesothelioma (MPM) is an incurable cancer of the pleura that can be difficult to diagnose. Biomarkers for an easier and/or earlier diagnosis are needed. Approximately 90% of MPM patients develop a pleural effusion (PE). PEs are ideal sources of biomarkers as the fluid would almost always require drainage for diagnostic and/or therapeutic reasons. However, differentiating MPM PE from PE caused by other diseases can be challenging. MicroRNAs are popular biomarkers given their stable expression in tissue and fluid. MicroRNAs have been analysed in PE cytology samples for the diagnosis of MPM but have not been measured in frozen/fresh PE. We hypothesise that microRNAs expressed in PE are biomarkers for MPM. TaqMan OpenArray was used to analyse over 700 microRNAs in PE cells and supernatants from 26 MPMs and 21 other PE-causing diseases. In PE cells, combining miR-143, miR-210, and miR-200c could differentiate MPM with an area under the curve (AUC) of 0.92. The three-microRNA signature could also discriminate MPM from a further 40 adenocarcinomas with an AUC of 0.9887. These results suggest that the expression of miR-143, miR-210, and miR-200c in PE cells might provide a signature for diagnosing MPM.

The Role of Ancillary Techniques in Pulmonary Cytopathology

Ancillary techniques play an essential role in pulmonary cytopathology. Immunoperoxidase and special stains are by far the most common ancillary techniques used in cytopathology; however, the role of molecular diagnosis is growing, especially in the fields of pulmonary oncology and infectious disease. In this article, we review the uses of ancillary techniques in lung tumor diagnosis, lung tumor classification, predictive marker determination, primary versus metastasis differential diagnosis, and infectious organism detection.

Molecular pathways and diagnosis in malignant mesothelioma: A review of the 14th International Conference of the International Mesothelioma Interest Group

The pathologist plays a central role in the diagnosis and management of malignant mesothelioma, including definitive tissue-based diagnosis in conjunction with clinical and radiographic data; diverse ancillary studies of diagnostic, prognostic, and predictive importance; and research efforts to better define the pathobiology of mesothelioma and develop novel clinical applications. The pivotal role of pathology in care of mesothelioma patients was on display at the recent meeting of the International Mesothelioma Interest Group (iMig) in Ottawa, Canada. This review summarizes the key findings of the "Molecular Pathways and Diagnosis in Malignant Mesothelioma" plenary session, including a large multi-institutional validation of a composite nuclear grading system for pleural mesothelioma, including incorporation of tumor necrosis as an additional independent prognostic factor; the correlation between nuclear grading in small biopsies and paired resection specimens in pleural mesothelioma; a multi-institutional study of important clinical and pathologic prognostic factors in peritoneal mesothelioma; the diagnostic role of HEG1 immunohistochemistry as a highly sensitive and specific marker of mesothelial lineage; the prevalence and diagnostic significance of MET protein overexpression in mesothelioma, as well as the correlation between MET protein overexpression and MET gene amplification; and the prognostic role of EZH2 protein overexpression in mesothelioma, together with data indicating an important pathogenic role for EZH2 in mesothelioma tumorigenesis. Special consideration is given to the convergence of diagnostic, prognostic, and predictive tools and their role in guiding highly personalized patient-centered management, and to the translation of novel research findings to practical techniques for routine pathologic practice.

Highlights of the 14th international mesothelioma interest group meeting: Pathologic separation of benign from malignant mesothelial proliferations and histologic/molecular analysis of malignant mesothelioma subtypes

OBJECTIVES

The separation of benign from malignant mesothelial proliferations and exact subclassification of mesothelioma subtypes is crucial to determining patient care and prognosis but morphologically can be very difficult.

METHODS

This session of the 2018 IMIG meeting addressed these problems.

RESULTS

A new immunohistochemical marker, methylthioadenosine phosphorylase, was shown to correlate well with CDKN2A FISH and is cheaper and faster to run. A 117 gene expression panel also provided good separation on both tissue biopsy and cytology samples. Review of a series of mesotheliomas thought to be biphasic produced only a moderate level of agreement among expert pathologists with some cases being classified as purely epithelioid or sarcomatoid; these classifications had prognostic significance. The entity called transitional mesothelioma was found to behave exactly like sarcomatoid mesothelioma. RNA-seq analysis of a large series of mesotheliomas from a public database showed that, genetically, the morphologic breakdown into epithelioid, sarcomatoid, or biphasic mesotheliomas is artificial because there is a continuous spectrum of genomic changes. There are now criteria for the diagnosis of mesothelioma in situ and this is potentially important, since such cases might be curable.

CONCLUSIONS

This session documented new morphological and molecular approaches to separating benign from malignant mesothelial proliferations and to subclassifying malignant mesoteheliomas in clinical relevant ways.

Updates in Effusion Cytology

Effusion cytology plays multiple roles in the management of benign and malignant disease, from primary diagnosis to tissue allocation for ancillary diagnostic studies and biomarker testing of therapeutic targets. This article summarizes recent advances in pleural effusion cytology, with a focus on the practical application of immunohistochemical markers, cytogenetic techniques, flow cytometry, and molecular techniques for the diagnosis and management of primary and secondary neoplasms of the pleura.

A proposal of Brazilian Society of Surgical Oncology (BSSO/SBCO) for standardizing cytoreductive surgery (CRS) plus hyperthermic intraperitoneal chemotherapy (HIPEC) procedures in Brazil: pseudomixoma peritonei, appendiceal tumors and malignant peritoneal mesothelioma

Cytoreductive surgery plus hypertermic intraperitoneal chemotherapy has emerged as a major comprehensive treatment of peritoneal malignancies and is currently the standard of care for appendiceal epithelial neoplasms and pseudomyxoma peritonei syndrome as well as malignant peritoneal mesothelioma. Unfortunately, there are some worldwide variations of the cytoreductive surgery and hypertermic intraperitoneal chemotherapy techniques since no single technique has so far demonstrated its superiority over the others. Therefore, standardization of practices might enhance better comparisons between outcomes. In these settings, the Brazilian Society of Surgical Oncology considered it important to present a proposal for standardizing cytoreductive surgery plus hypertermic intraperitoneal chemotherapy procedures in Brazil, with a special focus on producing homogeneous data for the developing Brazilian register for peritoneal surface malignancies.

Current status of malignant mesothelioma with liver involvement in China: A brief report and review of the literature

Primary and secondary intrahepatic malignant mesothelioma (PIHMM & SIHMM) caused by Peritoneal mesothelioma (PM) are extremely rare tumors and their clinicopathological characteristics remain unclear. The current study presented a case of a 63-year-old female with PIHMM and a literature review of Chinese case reports of SIHMM and PIHMM was performed. The patient received curative left hemihepatectomy because of a 5.5 × 5.0 × 4.0 cm mass occupying the II, III and the lateral portion of the IV segments and meanwhile tightly infiltrating the diaphragm (yellow arrow) was also observed. The pathological diagnosis was epithelial type PIHMM. Immunohistochemistry revealed that the tumor was positive for Calretinin, CK5/6, WT-1 and D2-40(N). The literature review included 11 studies and 6 case reports with a total of 293 PM patients accompanied with 31 SIHMM cases and then 3 case reports of PIHMM. SIHMM and PIHMM are extremely rare, easy to misdiagnose malignant tumors. Immunohistochemistry should be performed strictly in accordance with guidelines, which is crucial for pathological diagnosis. Comprehensive treatment of surgery combined with chemotherapy are mainstream methods for SIHMM and PIHMM. Also, exact survival data should be carefully explored so that objective evaluation of the efficacy of the treatment could be achieved.

Endocytoscopy for in situ real-time histology of oral mucosal lesions

This study investigated the utility of endocytoscopy, a novel emerging endoscopic system, for in situ real-time histology of oral mucosal lesions. Endocytoscopy involves the use of a contact light microscopy system with 380-fold magnification. With the development of endoscopic instruments, it has become possible to observe the abnormal microvascular and capillary patterns of tumour cells. The resolution of the endoscopic image is improved in situ, and a more detailed diagnosis is possible. In this study, endocytoscopy along with other diagnostic modalities was used in nine patients. Normal mucous membranes and oral malignant lesions were observed. Endocytoscopy enabled the pathological diagnosis of oral malignancies in situ and the observation of both structural and cytological atypia. In the future, it is expected that pathological diagnoses will be made in situ by direct viewing of living cells. This technique has the potential to allow an 'optical biopsy'.

On the diagnosis of malignant pleural mesothelioma: A necropsy-based study of 171 cases (1997–2016)

Background:

Malignant pleural mesothelioma (MPM) diagnosis is known to be difficult. We report on the diagnostic elements available in life in an MPM necropsy case series and describe the frequency of non-neoplastic asbestos-related diseases as biological exposure indices.

Methods:

We reviewed pathologic and clinical records of an unselected series of autopsies (1977–2016) in patients with MPM employed in the Monfalcone shipyards or living with shipyard workers. We assessed the consistency with autopsy results of diagnoses based on, respectively, radiologic, cytologic, and histologic findings, with and without immunophenotyping.

Results:

Data on 171 cases were available: for 169, autopsy confirmed the MPM diagnosis. In life, 119 cases had histologic confirmation of diagnosis, whereas 7 were negative; all cases without immunophenotypization were autoptic MPMs. Cytology alone had been positive in 18 autoptic MPM cases, negative in 14. Radiologic imaging alone had been positive in another 16, negative in 11. In the 2 cases not confirmed at autopsy, MPM had been suspected by chest computed tomography only. Bilateral pleural plaques were found in 144 and histologic evidence of asbestosis in 62 cases.

Conclusions:

Autopsies confirmed 169/171 cases, including cases that would not be considered as certain based on diagnosis in life. Radiologic imaging, cytologic examination of pleural effusions, or both combined had low sensitivity but high positive predictive value: when they are positive, proceeding to thoracoscopy should be justified. MPM has been correctly diagnosed even without immunohistochemistry. The prevalence of pleural plaques and asbestosis was high due to severity of asbestos exposures in these cases.

The pathological and molecular diagnosis of malignant pleural mesothelioma: a literature review

Malignant pleural mesothelioma (MPM), an asbestos-induced tumor, represents significant diagnostic challenges for pathologists. Its histological diagnosis is stepwise and should be based on morphological assessment, supported by clinical and radiological findings, and supplemented with immunohistochemistry (IHC) and, more recently, molecular tests. The main diagnostic dilemmas are the differential diagnoses with benign mesothelial proliferations and other pleural malignant tumors. The present review is an update regarding the morphological, immunohistochemical, and molecular features with respect to MPM diagnosis. Data sources include a survey of the biomedical literature from PubMed (http://www.ncbi.nlm.nih.gov/pubmed) and textbooks focusing on the pathological diagnosis of MPM and associated immunohistochemical and molecular markers. The histological findings of MPM could facilitate its diagnosis and provide important prognostic information. The immunohistochemical approach should rest on the application of a panel including positive (mesothelial-related) and negative markers with greater than 80% sensitivity and specificity, which need to be selected based on morphology and clinical information. Moreover, in challenging cases, fluorescent in situ hybridization (FISH) testing for the p16 deletion and IHC to evaluate the loss of BRCA1-associated protein 1 (BAP1) expression could be useful in distinguishing benign from malignant pleural proliferations.

Targeting microRNA to improve diagnostic and therapeutic approaches for malignant mesothelioma

Malignant mesothelioma is an aggressive and often fatal cancer associated with asbestos exposure. The disease originates in the mesothelial lining of the serosal cavities, most commonly affecting the pleura. Survival rates are low as diagnosis often occurs at an advanced stage and current treatments are limited. Identifying new diagnostic and therapeutic targets for mesothelioma remains a priority, particularly for the new wave of victims exposed to asbestos through do-it-yourself renovations and in countries where asbestos is still mined and used. Recent advances have demonstrated a biological role for the small but powerful gene regulators microRNA (miRNA) in mesothelioma. A number of potential therapeutic targets have been identified. MiRNA have also become popular as potential biomarkers for mesothelioma due to their stable expression in bodily fluid and tissues. In this review, we highlight the current challenges associated with the diagnosis and treatment of mesothelioma and discuss how targeting miRNA may improve diagnostic, prognostic and therapeutic approaches.

Novel systemic therapy against malignant pleural mesothelioma

Malignant pleural mesothelioma is an aggressive tumor of the pleura with an overall poor prognosis. Even with surgical resection, for which only a subset of patients are eligible, long term disease free survival is rare. Standard first-line systemic treatment consists of a platinum analog, an anti-metabolite, and sometimes anti-angiogenic therapy, but there is currently no well-established standard therapy for refractory or relapsed disease. This review focuses on efforts to develop improved systemic therapy for the treatment of malignant pleural mesothelioma (MPM) including cytotoxic systemic therapy, a variety of tyrosine kinase inhibitors and their downstream effector pathways, pharmacologic targeting of the epigenome, novel approaches to target proteins expressed on mesothelioma cells (such as mesothelin), arginine depletion therapy, and the emerging role of immunotherapy. Overall, these studies demonstrate the challenges of improving systemic therapy for MPM and highlight the need to develop therapeutic strategies to control this disease.

Diagnostic Usefulness of Claudin-3 and Claudin-4 for Immunocytochemical Differentiation between Metastatic Adenocarcinoma Cells and Reactive Mesothelial Cells in Effusion Cell Blocks

OBJECTIVE

Claudin-3 and claudin-4 have recently been reported as promising targets for the detection and diagnosis of cancer. This study was designed to evaluate the diagnostic value of claudin-3 and claudin-4 immunoreactivity to distinguish metastatic adenocarcinoma cells (MAC) from reactive mesothelial cells (RMC) in effusions.

STUDY DESIGN

Claudin-3 and claudin-4 immunocytochemical staining was performed on 234 cell block specimens, including 194 malignant effusions with MAC and 40 benign effusions with RMC. Any degree of membranous staining was considered positive.

RESULTS

Claudin-3 was positive in 190 (97.9%) out of 194 cases with MAC and in 3 (7.5%) out of 40 cases with RMC. Claudin-4 immunoreactivity was seen in all 194 (100%) cases with MAC and in 11 (27.5%) out of 40 cases with RMC. In all claudin-3- or claudin-4-positive RMC samples, the area of positive staining was <25% of the cells. Claudin-3 and claudin-4 efficiently discriminated between MAC and RMC (p < 0.001 for both), and claudin-3 was more specific than claudin-4 in differentiating between MAC and RMC (p < 0.05).

CONCLUSION

These results suggest that claudin-3 and claudin-4 are good candidates to be included as MAC markers in the panel of antibodies to distinguish MAC from RMC in effusion specimens.