Low homozygous/high heterozygous deletion status by p16 FISH correlates with a better prognostic group than high homozygous deletion status in malignant pleural mesothelioma

Pleural mesothelioma in situ : a comprehensive review

Pleural mesothelioma is a rare and aggressive cancer that affects the pleura. In recent years, there has been increasing interest and attention in detecting and diagnosing early-stage or precancerous forms of mesothelioma because of its severe prognosis and short life expectancy at the time of diagnosis. Mesothelioma in situ represents a clear opportunity to improve and innovate the diagnostic approach and the multimodality treatment of mesothelioma: the diagnosis of pleural mesothelioma at the 'in-situ phase' means early disease detection and thus paves the way to new possible curable strategies. Since 2021, when mesothelioma in situ was finally identified and described as a new histological entity, its diagnosis and management became a challenge and the subject of ongoing research; several aspects remain open and still outstanding as regards diagnostic techniques, time and probability of progression, need for and methods of follow up, aggressive and early surgery. This narrative review aims to provide a comprehensive overview of mesothelioma in situ covering its definition, risk factors, diagnostic criteria, and tricky aspects of early detection. It also highlights its clinical significance, new perspectives, and potential future indications in the context of pleural mesothelioma multidisciplinary management.

Detailed clinical course of a patient with rapidly progressing sarcomatoid pleural mesothelioma without p16 deletion with systemic haematogenous metastasis to soft tissues

Sarcomatoid mesothelioma is difficult to differentiate from other mesotheliomas. Here, we describe the case of a man in his early 80s with sarcomatoid mesothelioma and a history of asbestos exposure. He initially presented with right-sided chest pain and was examined. Right-sided pleural effusion was detected; therefore, he was hospitalised. Based on the observed pleural effusion and biopsy result, the presence of a malignant tumour was excluded; hence, he was diagnosed with benign asbestos pleurisy. He subsequently developed left-sided pleural effusion, masses and lung nodules, and died 9.5 months after the initial examination. A definitive diagnosis of sarcomatoid mesothelioma with rapid systemic progression was established after detailed investigations using autopsy specimens. This rare case of mesothelioma-without p16 deletion (detected using fluorescence in situ hybridisation)-presented differently from the usual sarcomatoid mesothelioma.

Diffuse Pleural Mesothelioma: Advances in Molecular Pathogenesis, Diagnosis, and Treatment

Diffuse pleural mesothelioma (DPM) is a highly aggressive malignant neoplasm arising from the mesothelial cells lining the pleural surfaces. While DPM is a well-recognized disease linked to asbestos exposure, recent advances have expanded our understanding of molecular pathogenesis and transformed our clinical practice. This comprehensive review explores the current concepts and emerging trends in DPM, including risk factors, pathobiology, histologic subtyping, and therapeutic management, with an emphasis on a multidisciplinary approach to this complex disease.

Sarcomatoid mesothelioma diagnosed in a patient with mesothelioma in situ: a case report on morphologic differences after 9-month interval with details analysis of cytology in early-stage mesothelioma

BACKGROUND

Overlapping morphological features of mesothelial cells have been rendered it difficult to distinguish between reactive and malignant conditions. The development of methods based on detecting genomic abnormalities using immunohistochemistry and fluorescence in situ hybridization have contributed markedly to solving this problem. It is important to identify bland mesothelioma cells on cytological screening, perform efficient genomic-based testing, and diagnose mesothelioma, because the first clinical manifestation of pleural mesothelioma is pleural effusion, which is the first sample available for pathological diagnosis. However, certain diagnostic aspects remain challenging even for experts.

CASE PRESENTATION

This report describes a case of a 72-year-old man with a history of asbestos exposure who presented with pleural effusion as the first symptom and was eventually diagnosed as mesothelioma. Mesothelioma was suspected owing to prominent cell-in-cell engulfment in mesothelial cells on the first cytological sample, and the diagnosis of mesothelioma in situ was confirmed by histology. Unexpectedly, sarcomatoid morphology of mesothelioma was found in the second pathology samples 9 months after the first pathological examination. Both the mesothelioma in situ and invasive lesion showed immunohistochemical loss of methylthioadenosine phosphorylase (MTAP) and homozygous deletion of cyclin dependent kinase inhibitor 2A (CDKN2A) on fluorescence in situ hybridization. The patient received medication therapy but died of disease progression 12 months after the diagnosis of the sarcomatoid morphology of mesothelioma.

CONCLUSION

Our case suggests that cell-in-cell engulfment can be conspicuous in early-stage mesothelioma with inconspicuous nuclear atypia and few multinucleated cells. In addition, the presence of MTAP loss and CDKN2A homozygous deletion are suspected to be involved in early formation to invasive lesions and/or sarcomatoid morphology. We believe that it is important to consider genetic abnormalities when deciding on individual patient management. Furthermore, cases of mesothelioma, even those of an in situ lesion, with MTAP loss and/or CDKN2A deletion should be carefully followed up or subjected to early treatment.

Evaluation of MTAP and p16 immunohistochemical deficiency as surrogate marker for CDKN2A/B homozygous deletion in gliomas

Homozygous deletion (HD) of the CDKN2A/B locus has emerged as an unfavourable prognostic marker in diffuse gliomas, both IDH-mutant and IDH-wild-type. Testing for CDKN2A/B deletions can be performed by a variety of approaches, including copy number variation (CNV) analysis based on gene array analysis, next generation sequencing (NGS) or fluorescence in situ hybridisation (FISH), but questions remain regarding the accuracy of testing modalities. In this study, we assessed: (1) the utility of S-methyl-5'-thioadenosine phosphorylase (MTAP) and cellular tumour suppressor protein pl61NK4a (p16) immunostainings as surrogate markers for CDKN2A/B HD in gliomas, and (2) the prognostic value of MTAP, across different histological tumour grades and IDH mutation status. One hundred consecutive cases of diffuse and circumscribed gliomas (Cohort 1) were collected, in order to correlate MTAP and p16 expression with the CDKN2A/B status in the CNV plot of each tumour. IDH1 R132H, ATRX and MTAP immunohistochemistry was performed on next generation tissue microarrays (ngTMAs) of 251 diffuse gliomas (Cohort 2) for implementing survival analysis. Complete loss of MTAP and p16 by immunohistochemistry was 100% and 90% sensitive as well as 97% and 89% specific for CDKN2A/B HD, respectively, as identified on CNV plot. Only two cases (2/100) with MTAP and p16 loss of expression did not demonstrate CDKN2A/B HD in CNV plot; however, FISH analysis confirmed the HD for CDKN2A/B. Moreover, MTAP deficiency was associated with shortened survival in IDH-mutant astrocytomas (n=75; median survival 61 vs 137 months; p<0.0001), IDH-mutant oligodendrogliomas (n=59; median survival 41 vs 147 months; p<0.0001) and IDH-wild-type gliomas (n=117; median survival 13 vs 16 months; p=0.011). In conclusion, MTAP immunostaining is an important complement for diagnostic work-up of gliomas, because of its excellent correlation with CDKN2A/B status, robustness, rapid turnaround time and low costs, and provides significant prognostic value in IDH-mutant astrocytomas and oligodendrogliomas, while p16 should be used cautiously.

Sarcomatoid Mesothelioma with Bland Histologic Features: A Potential Pitfall in Diagnosis

Sarcomatoid mesotheliomas can be challenging to diagnose on small biopsy specimens, where limited material may preclude definitive assessment of invasion and lesional cells can have relatively bland cytology with no mesothelial marker expression. We report a case of a patient who presented with a pleural effusion and had subsequent pleural biopsy that showed a bland, uniform spindle cell proliferation in a mildly myxoid background. There was little if any collagen; no chest wall, soft tissue, or fat; and mesothelial markers were negative. The cells were positive for pancytokeratin and GATA3 by immunohistochemistry, and in situ hybridization showed a "negative" result for homozygous loss of CDKN2A; however, there was partial (heterozygous) loss of one allele. A diagnosis of atypical spindle cell proliferation was made based on these findings. Several months later, the patient had a repeat pleural biopsy that showed spindled cells with more pleomorphism, areas of invasion into the chest wall, and the same partial loss of CDKN2A, consistent with a sarcomatoid mesothelioma. This case underscores the challenges present on small biopsy specimens, the fact that sarcomatoid mesotheliomas can be relatively bland appearing with focal pleomorphism, and that heterozygous loss of CDKN2A should be considered a positive result indicative of a neoplastic process.

Novel and Future Treatment Options in Mesothelioma: A Systematic Review

Mesothelioma is a rare tumor, frequently associated with asbestos exposure, arising from pleura and peritoneum. Traditionally, diagnosis and treatment have been difficult in a clinical setting. The treatment is based on a trimodal approach involving surgery, chemotherapy, and radiotherapy. The introduction of chemotherapy improved the overall survival. However, the regimen of pemetrexed/cisplatin doublet has not been changed as a standard treatment since 2004. Novel combinations of ipilimumab and nivolumab have only been approved for clinical use in late 2020. The aim of this review was to systematically summarize findings on novel treatment options in mesothelioma. We searched available medical databases online, such as PubMed and Clinicaltrials.gov, to systematically review the literature on novel approaches in immunotherapy, vaccines, and Chimeric Antigen Receptor (CAR)-T cell therapy in mesothelioma. We manually screened 1127 articles on PubMed and 450 trials on ClinicalTrials.gov, and 24 papers and 12 clinical trials published in the last ten years were included in this review. Immunotherapy that was swiftly introduced to treat other thoracic malignancies was slow to reach desirable survival endpoints in mesothelioma, possibly due to limited patient numbers. Novel treatment approaches, such as CAR-T cell therapy, are being investigated. As the incidence of mesothelioma is still rising globally, novel treatment options based on a better understanding of the tumor microenvironment and the genetic drivers that modulate it are needed to support future precision-based therapies.

Sarcomatoid mesothelioma originating from mesothelioma in situ: are methylthioadenosine phosphorylase loss and CDKN2A homozygous deletion poor prognostic factors for preinvasive mesothelioma?

The diagnosis of mesothelioma in situ (MIS) is challenging with conventional diagnostic approaches. Although recent advances in genomic-based assays have made it possible to diagnose MIS, the prognosis, treatment indications, and prognostic factors remain unclear. Previous reports have shown that MIS progresses to invasive mesothelioma; however, to the best of our knowledge, progression to sarcomatoid mesothelioma has not yet been reported. A 73-year-old man was diagnosed with MIS associated with methylthioadenosine phosphorylase (MTAP) loss and a CDKN2A homozygous deletion. Strikingly, pathological examination revealed that the MIS lesion had progressed to sarcomatoid mesothelioma. In analyses of previously reported cases and our case, MIS with a CDKN2A homozygous deletion or MTAP loss progressed to invasive mesothelioma earlier than that without them, indicating that a CDKN2A homozygous deletion and MTAP loss could be poor prognostic factors. Genomic analyses might be useful for predicting the prognosis of MIS and contributing to an optimal treatment.

Comparison of Nuclear Grade, Necrosis, and Histologic Subtype Between Biopsy and Resection in Pleural Malignant Mesothelioma: An International Multi-Institutional Analysis

OBJECTIVES

Numerous studies on malignant mesothelioma (MM) highlight the prognostic importance of histologic subtype, nuclear grade, and necrosis. This study compares these parameters in paired biopsy and resection specimens of pleural MM.

METHODS

Histologic subtype, percentage of epithelioid morphology, nuclear grade, and the presence or absence of necrosis were compared in 429 paired biopsies and resection specimens of pleural MM from 19 institutions.

RESULTS

Histologic subtype was concordant in 81% of cases (κ = 0.58). When compared with resection specimens, epithelioid morphology at biopsy had a positive predictive value (PPV) of 78.9% and a negative predictive value (NPV) of 93.5%; sarcomatoid morphology showed high PPV (92.9%) and NPV (99.3%), and biphasic morphology PPV was 89.7% and NPV was 79.7%. Agreement of the percentage of epithelioid morphology was fair (κ = 0.27). Nuclear grade and necrosis were concordant in 75% (κ = 0.59) and 81% (κ = 0.53) of cases, respectively. Nuclear grade showed moderate (κ = 0.53) and substantial (κ = 0.67) agreement from patients with and without neoadjuvant therapy, respectively, and necrosis showed moderate (κ = 0.47 and κ = 0.60) agreement, respectively, in the same subsets of paired specimens.

CONCLUSIONS

Paired biopsy-resection specimens from pleural MM show overall moderate agreement in pathologic parameters. These findings may help guide postbiopsy management and triage of patients with MM.

Short 57 kb CDKN2A FISH probe effectively detects short homozygous deletion of the 9p21 locus in malignant pleural mesothelioma

Homozygous deletion (homo-d) of the cyclin-dependent kinase inhibitor 2A (CDKN2A) gene is frequently found in malignant pleural mesothelioma (MPM). Fluorescence in situ hybridization (FISH) is commonly used to detect chromosomal deletion, and sometimes reveals more frequent heterozygous deletion (hetero-d) compared with homo-d. In clinical practice, such CDKN2A FISH results belong to the 'borderline' homo-d rate, which makes it difficult to definitively diagnose MPM. Microdeletion, [<200 kilobase (kb)], can induce a 'pseudo' hetero-d signal in FISH assays with long probes owing to redundant probe reactivity. Thus, the present study hypothesized that shorter FISH probes can effectively detect the small deletion status of the CDKN2A gene and increase homo-d rate in MPM, which has high hetero-d and low homo-d status. The present study aimed to evaluate the effectiveness of a shorter CDKN2A FISH probe in diagnosing MPM. CDKN2A FISH with either a 222 kb long probe (L-probe) or a 57 kb short probe (S-probe) was performed in four MPM cases with high hetero-d and low homo-d patterns. Furthermore, immunohistochemistry for methylthioadenosine phosphorylase (MTAP) and quantitative (q)PCR analyses were performed to confirm the microdeletion of the 9p21 locus. The results demonstrated that all four MPM cases retained MTAP protein expression. CDKN2A FISH with L-probe revealed high hetero-d (cases 1-4; 73.3, 37.1, 59.2 and 64.8%, respectively) and low homo-d (cases 1-4; 12.1, 12.4, 25.4 and 22.2%, respectively). CDKN2A FISH with S-probe revealed high homo-d (cases 1-4; 96.8, 90.0, 87.5 and 82.6%, respectively), with low hetero-d (cases 1-4; 0.0, 1.2, 1.2 and 4.3%, respectively). qPCR analysis demonstrated no allele deletions of the MTAP gene and two-allele deletions of the CDKN2A gene in 3/4 cases. Taken together, these results suggest that the S-probe detects the short homo-d of the 9p21 locus more effectively than the L-probe in MPM. This can assist in solving diagnostic difficulties in cases involving high hetero-d with low homo-d.

Correlation of methylthioadenosine phosphorylase (MTAP) protein expression with MTAP and CDKN2A copy number in malignant pleural mesothelioma

AIMS

Methylthioadenosine phosphorylase (MTAP) immunohistochemical expression is a specific marker of CDKN2A deletion in malignant mesothelioma. However, the relationship of MTAP expression with MTAP copy number remains unexplored.

METHODS AND RESULTS

Forty malignant pleural mesotheliomas were characterised by targeted next-generation sequencing (29), single-nucleotide polymorphism microarray (seven), or both (four). MTAP and CDKN2A copy numbers were correlated with MTAP expression. Twenty-seven (68%) tumours showed CDKN2A deletion (14 heterozygous; 13 homozygous), of which 20 (74%) showed MTAP codeletion (15 heterozygous; five homozygous). No tumours showed MTAP deletion without CDKN2A codeletion. Loss of MTAP expression was seen in 16 (40%) tumours, and was 75% sensitive and 95% specific for MTAP deletion, and 59% sensitive and 100% specific for CDKN2A deletion. Nine of 40 (23%) tumours showed heterogeneous MTAP staining, and the percentage of tumour cells with MTAP loss correlated with molecular detection of MTAP deletion.

CONCLUSIONS

MTAP is frequently codeleted with CDKN2A in pleural mesothelioma. However, homozygous deletion of both genes occurs in a minority of tumours (5/40; 13%); CDKN2A deletion often co-occurs with heterozygous MTAP deletion or neutral MTAP copy number; and MTAP expression correlates inconsistently with heterozygous MTAP deletion. Correspondingly, MTAP immunohistochemistry is a highly specific but only moderately sensitive assay for CDKN2A deletion.

Sarcomatoid Mesothelioma: A CDKN2A molecular analysis of 53 cases with immunohistochemical correlation with BAP1

Fifty-three cases of sarcomatoid pleural mesothelioma were evaluated for CDKN2A (p16) homozygous deletion and correlated with BRCA-associated protein-1 (BAP1) expression by immunohistochemistry. The patients are 45 men and 8 women between the ages of 37 and 79 years (average age: 58 years), who presented with symptoms of chest pain, cough, and weight loss. Diagnostic imaging showed the presence of diffuse pleural thickening with encasement of the lung parenchyma in all the cases. All patients were surgically treated with extrapleural pneumonectomy. Loss of BAP1 reactivity was seen in 49 tumors and p16 homozygous deletion was seen in 41 tumors, while in 16 patients either BAP1 or p16 were noncontributory to the diagnosis of mesothelioma. However, we were able to detect a better survival rate in those patients in whom BAP1 was lost and p16 showed homozygous deletion. Our findings showed that even though the use of BAP1 and p16 are important tools in the diagnosis of mesothelioma, a proportion of cases still remains negative with approximately 30 % of the cases in which the concordance of BAP1 loss and p16 homozygous deletion will not be present. We consider that the final diagnosis of mesothelioma is best accomplished by a global interpretation of clinical, radiographic, and pathological features including immunohistochemistry and molecular studies.

Genomic-based ancillary assays offer improved diagnostic yield of effusion cytology with potential challenges in malignant pleural mesothelioma

BRCA1-associated protein 1 (BAP1) or methylthioadenosine phosphorylase (MTAP) immunohistochemistry (IHC) or 9p21 fluorescence in situ hybridization (FISH) are useful for the diagnosis of malignant pleural mesothelioma (MPM). However, the effect of these assays on the diagnostic yield of effusion cytology in MPM cases with suspicious cytomorphology or the diagnostic challenges in BAP1 or MTAP IHC have not been fully elucidated. Two cohorts of cytologic preparations obtained from pleural effusions were examined: MPM cases in cohort 1 were used to evaluate whether BAP1 or MTAP IHC or 9p21 FISH increase the diagnostic yield of effusion cytology; cohort 2 included cases suspicious for MPM, to which BAP1 or MTAP IHC was applied to clarify the challenges in the clinical assessment of these assays. In cohort 1 (n = 28), either assay elevated 62.5% of class II or III cases to class V. In cohort 2 (n = 139), 21.7% of BAP1 immunocytochemistry in smears and 10.6% of BAP1 IHC and 9.4% of MTAP IHC in cell blocks, were identified to be challenging. The application of genomic-based assays increased the diagnostic yield of effusion cytology in the diagnosis of MPM. However, diagnostic challenges limit the application of these assays in some cases.

HEG1, BAP1, and MTAP are useful in cytologic diagnosis of malignant mesothelioma with effusion

BACKGROUND

The specificity and sensitivity of HEG1 for malignant mesothelioma (MM) is high. The use of BAP1/MTAP immunohistochemistry (IHC) is recommended to separate benign and malignant mesothelial proliferations. We determined how ancillary techniques can be used for the cytological diagnosis of MM with effusion.

METHODS

Cell blocks from effusions from cases with MM, reactive mesothelial cells (RMCs), and carcinomas were analyzed by IHC with HEG1, BAP1, and MTAP and with homozygous deletion (HD) of CDKN2A by fluorescence in situ hybridization. Staining scores were calculated for IHC by adding the number of categories for the staining intensity and the staining extension.

RESULTS

HEG1 was positive in all (41/41) MMs, but negative in carcinomas, except for ovarian carcinomas. Overall 76.9% (20/26) of RMCs and 28.6% (6/21) of ovarian carcinomas expressed HEG1. BAP1 loss was found in 71.1% of MMs, but none was found in RMCs. MTAP loss was found in 76.2% of MMs, but none was found in RMCs. 73.9% of MMs harbored HD of CDKN2A. There was concordance between loss of MTAP and HD of CDKN2A in 95% of MMs.

CONCLUSION

HEG1 is a good marker for mesothelial differentiation in effusion cytology. HD of CDKN2A is frequently observed in cell blocks from effusions of MMs, and MTAP IHC may act as a surrogate for HD of CDKN2A. Cell block analysis is recommended for effusions of unknown origins with the following methods: IHC with HEG1 and claudin 4 to validate the mesothelial origin, followed by BAP1 and MTAP IHC to confirm malignancy.

Fluorescence in situ hybridization (FISH) provides estimates of minute and interstitial BAP1, CDKN2A, and NF2 gene deletions in peritoneal mesothelioma

The aim of this study was to assess the performance of fluorescence in situ hybridization (FISH) in identifying the copy number profiles of the three key peritoneal mesothelioma tumor suppressor genes BAP1, CDKN2A, and NF2, with particular emphasis on minute homozygous deletions, a copy number abnormality recently unveiled at the 3p21 (BAP1) chromosomal region using high-throughput methods. FISH was performed on 75 formalin-fixed-paraffin-embedded peritoneal mesotheliomas and recognized two types of monoallelic loss (monosomy, and hemizygous deletion) and two types of biallelic loss (canonical homozygous deletion with a complete loss of FISH signal and homozygous deletion with diminished signal). Diminished FISH signals revealed deletions occurring within the genomic region covered by the gene-specific probe and affected all three tumor suppressors. BAP1 homozygous deletions with diminished signal outnumbered canonical homozygous deletions (13 vs 3): conversely, canonical homozygous deletions were prevalent for CDKN2A (2 vs 14). Diminished signal homozygous deletion was the only pattern of biallelic loss observed for NF2 (2 cases). Hemizygous deletion mainly affected BAP1 (21 vs 6), while monosomy was prevalent for CDKN2A (14 vs 7) and particularly for NF2 where it accounts for all monoallelic losses. FISH/immunohistochemistry (BAP1, CDKN2A, and MTAP) correlation showed that all homozygous deletions, including those with diminished signals, resulted in a null BAP1 and CDKN2A immunophenotype but only canonical CDKN2A homozygous deletions resulted in MTAP loss of expression. BAP1 hemizygous deletion, but not monosomy, was also invariably associated with loss of protein expression whereas neither type of CDKN2A monoallelic loss correlated with p16 or MTAP immunohistochemistry. Array comparative genomic hybridization performed on a spontaneously emerging peritoneal mesothelioma cell line provided support for the interpretation of the FISH patterns and allowed us to extend the number of chromatin remodeling factors involved in mesothelioma to SETD7 and PCGF5, two previously unreported genes.

Hemizygous loss of NF2 detected by fluorescence in situ hybridization is useful for the diagnosis of malignant pleural mesothelioma

Neurofibromatosis type 2 (NF2) gene, a tumor suppressor gene located on chromosome 22q12.2, is frequently abnormal in mesothelioma. Recent studies have revealed the effectiveness of diagnostic assays for differentiating malignant pleural mesothelioma from reactive mesothelial hyperplasia. These include detection of homozygous deletion of the 9p21 locus by fluorescence in situ hybridization (FISH) (9p21 FISH), loss of expression of BAP1 as detected by immunohistochemistry, and loss of expression of methylthioadenosine phosphorylase (MTAP) as detected by immunohistochemistry. However, the application of FISH detection of NF2 gene deletion (NF2 FISH) in differentiation of malignant pleural mesothelioma from reactive mesothelial hyperplasia has not been fully evaluated. In this study, we investigated whether NF2 FISH, either alone or in a combination with other diagnostic assays (9p21 FISH, MTAP immunohistochemistry, and BAP1 immunohistochemistry), is effective for distinguishing malignant pleural mesothelioma from reactive mesothelial hyperplasia. This study cohort included malignant pleural mesothelioma (n = 47) and reactive mesothelial hyperplasia cases (n = 27) from a period between 2001 and 2017. We used FISH to examine deletion status of NF2 and 9p21 and immunohistochemistry to examine expression of MTAP and BAP1 in malignant pleural mesothelioma and in reactive mesothelial hyperplasia. Hemizygous NF2 loss (chromosome 22 monosomy or hemizygous deletion) was detected in 25 of 47 (53.2%) mesothelioma cases. None of the mesothelioma cases showed homozygous NF2 deletion. Hemizygous NF2 loss showed 53.2% sensitivity and 100% specificity in differentiating malignant pleural mesothelioma from reactive mesothelial hyperplasia. A combination of NF2 FISH, 9p21 FISH, and BAP1 immunohistochemistry yielded greater sensitivity (100%) than that detected for either diagnostic assay alone (53.2% for NF2 FISH, 78.7% for 9p21 FISH, 70.2% for MTAP immunohistochemistry, or 57.4% for BAP1 immunohistochemistry). Thus, NF2 FISH in combination with other diagnostic assays is effective for distinguishing malignant pleural mesothelioma from reactive mesothelial hyperplasia.

Application of immunohistochemistry in diagnosis and management of malignant mesothelioma

Immunohistochemistry plays an indispensable role in accurate diagnosis of malignant mesothelioma, particularly in morphologically challenging cases and in biopsy and cytology specimens, where tumor architecture is difficult or impossible to evaluate. Application of a targeted panel of mesothelial- and epithelial-specific markers permits correct identification of tumor lineage in the vast majority of cases. An immunopanel including two mesothelial markers (calretinin, CK5/6, WT-1, or D2-40) and two epithelial markers (MOC-31 and claudin-4) offers good sensitivity and specificity, with adjustments as appropriate for the differential diagnosis. Once mesothelial lineage is established, malignancy-specific studies can help verify a diagnosis of malignant mesothelioma. BAP1 loss, CDKN2A homozygous deletion, and MTAP loss are highly specific markers of malignancy in a mesothelial lesion, and they attain acceptable diagnostic sensitivity when applied as a diagnostic panel. Novel markers of malignancy, such as 5-hmC loss and increased EZH2 expression, are promising, but have not yet achieved widespread clinical adoption. Some diagnostic markers also have prognostic significance, and PD-L1 immunohistochemistry may predict tumor response to immunotherapy. Application and interpretation of these immnuomarkers should always be guided by clinical history, radiographic findings, and above all histomorphology.

Differential expression of immune-related genes in head kidney and spleen of cobia (Rachycentron canadum) having Streptococcus dysgalactiae infection

Streptococcus dysgalactiae is a gram-positive bacterium and a harmful aquaculture pathogen. To investigate the immune response against S. dysgalactiae, we performed transcriptome analysis of the head kidney and spleen of cobia (Rachycentron canadum) using RNA-seq. Total RNA was extracted from the head kidney and spleen of cobia, 1 and 2 days after treatment with S. dysgalactiae or control PBS. After RNA purification and cDNA library generation, sequencing was performed using the Illumina HiSeq™ 4000 platform. The filtering and de novo assembling transcripts were annotated using several databases. To identify differentially expressed genes (DEGs) between the S. dysgalactiae and PBS groups, the mapped values of fragments per kilobase of transcripts per million fragments were calculated. After de novo assembly, a total of 106,984 transcripts were detected, with an N50 of 3020 bp. These transcripts were annotated and categorised into a total of 7608 genes based on the KEGG pathway database. DEGs (2-fold difference) were calculated by comparing the S. dysgalactiae and PBS control group gene expression levels at each time point. The DEGs were mainly annotated into signal transduction and immune system categories, based on the KEGG database. The DEGs were significantly enriched in the immune-related pathways - "cytokine-cytokine receptor interaction", "complement and coagulation cascades", and "hematopoietic cell linage". In this study, immune-related genes responding to S. dysgalactiae were detected, and several immune system pathways were categorized. We identified the IL17C-related pathway for inducing the expression of pro-inflammatory cytokine genes (IL-1β, IL-6, and IFNγ). Additionally, neutrophil-related genes (CSF3, CD121, and CD114) were induced in the spleen after S. dysgalactiae infection. It was suggested that these pathways contribute to immune responses against S. dysgalactiae infection. The data revealed in this study may offer improved strategies against S. dysgalactiae infection in cobia.

Pathologic Considerations and Standardization in Mesothelioma Clinical Trials

The accurate diagnosis of mesothelioma is critical for the appropriate clinical management of this cancer. Many issues complicate making the diagnosis of mesothelioma including the presence of reactive mesothelial cells in benign pleural effusions, the heterogeneity of mesothelioma histopathology, the relatively high incidence of other epithelial malignancies that metastasize to the pleura, and primary sarcomas that arise within the pleura. Given the rapidly evolving field of molecular profiling and the need for translational correlates in mesothelioma clinical trials, the National Cancer Institute (NCI)-International Association for the Study of Lung Cancer-Mesothelioma Applied Research Foundation Clinical Trials Planning Meeting was convened in March 2017 to develop a consensus on standard pathology guidelines for future NCI-sponsored clinical trials in mesothelioma. This consensus statement covers recommendations for specimen handling, pathologic classification and diagnosis, biobanking, and tissue correlative studies.

[Clinical and pathological profile of the pleural malignant mesothelioma: A retrospective study about 30 cases]

BACKGROUND

The malignant pleural mesothelioma (MPM) is a rare tumour usually associated to asbestos exposure. The delay between the exposure and the occurrence of the cancer can reach 40 years. This caused the pick of incidence described in many countries including Tunisia. The diagnosis is suspected based on clinical features but positive diagnosis is microscopic. Our aim was to describe the clinical and microscopic features of MPM through a single institution experience.

PATIENTS AND METHODS

We conducted a retrospective study about 30 MPM diagnosed over a 20-year-period (1995-2015). We included only patients with complete records including clinical, radiologic and microscopic features. All the microscopic diagnoses were reviewed by 2 pathologists. A mean of 12 slides per case was reviewed. The diagnosis was based on the 2015 WHO classification.

RESULTS

The mean age of the patients was 61 years, average 22 to 80 years. The sex ratio was 6,5. An asbetose exposition was reported in 21 cases. The most frequent symptoms was chest pain reported in 25 cases. Physical exam was normal in 9 cases. It revealed pleural syndorm in most patients (60 %). Imaging findings consisted mainly in diffuse pleural thickening in 17 cases. Twelve tumours were classified as stage I, 3 stage II, 14 stage III et 1 stage IV. Pleural biopsy was performed using needle in 18 cases, through thoracoscopy in 16 cases, thoracotomy in 3 cases and allowed the diagnosis in respectively 7 cases/18, 16 cases/16 and 3 cases/3. A lymph node biopsy was performed through mediastinoscopy in one case and yelded the diagnosis. The diagnosis was performed on surgical specimen in 2 patients: one bullectomy and one right upper lobectomy. The microscopic exam concluded to an EM in 17 cases, sarcomatoid mesothelioma (SM) in 4 cases and biphasic mesothelioma (BM) in 9 cases. Pan-cytokeratin antibody was used in all cases in association with 2 antibodies with positive diagnostic value and 2 antibodies with negative diagnostic value. It was repeated in 15 cases and the most used antibodies were the anti-calretinin and the TTF1. This was due to the lack of fixation in one case and in order to reach a quality criteria in the other cases. Surgical resection was possible in 2 patients. 15 patients were lost of view after a mean follow-up period of 3 months. Thirteen patients died before or during the follow-up.

CONCLUSION

This work was about a Tunisian experience in the diagnosis and management of MPM. The major limits faced were the incomplete databases, the small number of patients included. Microsocpic positive diagnosis necessitates a degree of expertise and every laboratory has to determine the most valuable antibodies through its experience in order to optimize the diagnosis and to reduce the delay of diagnosis.

Large-scale copy number analysis reveals variations in genes not previously associated with malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive tumor that is often causally associated with asbestos exposure. Comparative genomic hybridization techniques and arrays demonstrated a complex set of copy number variations (CNVs) in the MPM-genome. These techniques however have a limited resolution, throughput and flexibility compared to next-generation sequencing platforms.

In this study, the presence of CNVs in the MPM-genome was investigated using an MPM-cohort (N = 85) for which genomic microarray data are available through ‘The Cancer Genome Atlas’ (TCGA). To validate these results, the genomes of MPMs and matched normal samples (N = 21) were analyzed using low-pass whole genome sequencing on an ‘Illumina HiSeq’ platform. CNVs were detected using in-house developed analysis pipelines and frequencies of copy number loss and gain were calculated.

In both datasets, losses on chromosomes 1, 3, 4, 6, 9, 13 and 22 and gains on chromosomes 1, 5, 7 and 17 were found in at least 25% and 15% of MPMs, respectively. Besides the well-known MPM-associated genes, CDKN2A, NF2 and BAP1, other interesting cancer-associated genes were listed as frequently involved in a copy number loss (e.g. EP300, SETD2 and PBRM1). Moreover, four cancer-associated genes showed a high frequency of copy number gain in both datasets (i.e. TERT, FCGR2B, CD79B and PRKAR1A). A statistically significant association between overall survival and the presence of copy number loss in the CDKN2A-containing region was observed in the TCGA-set.

In conclusion, recurrent CNVs were detected in both datasets, occurring in regions harboring known MPM-associated genes and genes not previously linked to MPM.

Diagnostic accuracy of BRCA1-associated protein 1 in malignant mesothelioma: a meta-analysis

Background

Conventional measurements are not always helpful in the diagnosis of malignant mesothelioma (MM). Increasing studies indicate that loss of BRCA1–associated protein 1 (BAP1) detected by immunohistochemistry (IHC) is a useful diagnostic marker for MM. In this meta-analysis, we investigated the diagnostic accuracy of BAP1 in MM.

Results

In total, 12 eligible studies with a total of 1824 patients were selected. Results indicated that loss of BAP1 sustained a pooled sensitivity of 0.56 (95% CI, 0.50–0.62), specificity of 1.00 (95% CI, 0.95–1.00), PLR of 548.82 (95% CI, 11.31–2.7 × 104), NLR of 0.44 (95% CI, 0.39–0.50), DOR of 1247.78 (95% CI, 25.08 −6.2 × 104) in discriminating MM from non-MM. The AUC of 0.72, reflecting the SROC, indicated moderate diagnostic accuracy. Subgroup analysis showed that BAP1 detection in histological specimens owned the higher diagnostic performance than cytological ones. In addition, BAP1 showed superior diagnostic accuracy in epithelioid MM than biphasic or sarcomatoid MM.

Materials and Methods

PubMed, Embase and the Cochrane Library and reference lists of related articles were searched, and studies that evaluated the utility of BAP1 in MM were included. Data from eligible studies were pooled to estimate sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR). Summary receiver operating curves (SROC) was applied to estimate overall diagnostic accuracy.

Conclusions

Current meta-analysis indicates that detection of BAP1 by IHC is a useful diagnostic marker for MM. Loss of BAP1 almost provides confirming diagnosis for MM, while positive staining for BAP1 is not enough to exclude non-MM.