Spindle cell tumours of the pleura: a clinical, histological and comparative genomic hybridization analysis of 14 cases

Pulmonary sarcomatoid carcinoma: A rare case report, diagnostic dilemma and review of literature

RATIONALE

Pulmonary sarcomatoid carcinoma (PSC), a rare tumor, comprises 0.1% to 0.4% of all malignant lung tumors. Given the rarity of PSC, its clinical course, therapeutic guidelines, and patient outcomes remain largely unknown. Therefore, it is imperative to alert clinicians to this extremely rare and instructive early-onset cancer.

PATIENT CONCERNS

This report describes a 28-year-old woman with PSC, who was initially misdiagnosed with Whipple's disease. A conclusive diagnosis of PSC was made following careful clinical examination, imaging, and histopathological evaluation of the patient's biopsy sample. Radiological imaging revealed multiple nodules and mass formations in the left upper lobe of the patient's lung, with the largest measuring of 5.4 × 3.2 cm.

DIAGNOSIS

Histopathological examination indicated the presence of a malignant neoplasm associated with necrosis suggestive of sarcoma, which was pathologically staged as cT4N1M1.

INTERVENTIONS AND OUTCOMES

A regimen of doxorubicin and ifosfamide was administered therapeutically, resulting in a stable disease state.

LESSONS

The rarity and tumor origin challenge the diagnosis, which emphasizes the imperative role of histological examination, immunohistochemistry, and flow cytometry in achieving an accurate diagnosis. This report summarizes the existing publications to provide a comprehensive overview of PSC, including its clinical manifestations, radiographic imaging, pathologic features, diagnostic challenges, treatment strategies, and prognosis, and aims to improve the understanding of PSC.

Primary malignant epithelioid hemangioendothelioma of the pleura: A review and report of a novel case

Epithelioid hemangioendothelioma is considered an uncommon tumor originating from vascular tissues. Although this disease is an extremely rare malignant cancer, its pleural subtype is even less common. We discuss a 68‐year‐old man with isolated pleural epithelioid hemangioendothelioma, along with a literature review of all similar cases.

Approaches to Tumor Classification in Pulmonary Sarcomatoid Carcinoma

Pulmonary sarcomatoid carcinoma (PSC) is a heterogeneous category of primary lung cancer accounting from 0.3% to 3% of all primary lung malignancies. According to the most recent 2015 World Health Organization (WHO) classification, PSC includes several different variants of malignant epithelial tumors (carcinomas) histologically mimicking sarcomas showing or entirely lacking a conventional component of non-small cell lung cancer (NSCLC). Thus, this rare subheading of lung neoplasms includes pleomorphic carcinoma, spindle cell carcinoma, giant cell carcinoma, pulmonary blastoma, and carcinosarcoma. A diagnosis of PSC may be suspected on small biopsy or cytology, but commonly requires a surgical resection to reach a conclusive definition. The majority of patients with PSC consists of elderly, smoking men with a large, peripheral mass characterized by well-defined margins. However, presentation with a central, polypoid endobronchial lesion is well-documented, particularly in pleomorphic carcinoma and carcinosarcoma showing a squamous cell carcinoma component. As expected, PSC may pose diagnostic problems and immunohistochemistry is largely used when pathologists deal these tumors in routine practice. Indeed, PSC tends to overexpress molecules associated with the epithelial-to-mesenchymal transition, such as vimentin, but the panel of immunostains also includes epithelial markers (cytokeratins, EMA), TTF-1, p40 and negative markers (e.g., melanocytic, mesothelial and sarcoma-related primary antibodies). Although rare, PSC has increased their interest among oncologist community for different reasons: a. identification of the epithelial-to-mesenchymal phenomenon as a major mechanism of secondary resistance to tyrosine kinase inhibitors; b. over-expression of PD-L1 and effective treatment with immunotherapy; c. identification of c-MET exon 14 skipping mutation representing an effective target to crizotinib and other specific inhibitors. In this review, the feasibility of the diagnosis of PSC, its differential diagnosis and novel molecular findings characterizing this group of lung tumor are discussed.

Pleural Epithelioid Hemangioendothelioma: A Case Report and Literature Review

Epithelioid hemangioendothelioma (EHE) is a rare neoplasm of vascular origin that can arise in multiple and varied tissue sites. Pleural epithelioid hemangioendothelioma (PEH), a subtype of EHE, is particularly less reported. Herein, we describe a case of PEH presented with left-sided back pain in a 68-year-old female, and her chest CT scan revealed thickening of the left pleura and left pleural effusion, the histological diagnosis was confirmed by both conventional examination and immunohistochemistry. A literature search utilizing PubMed, Embase, Ovid and Cochrane, Wanfang and Chinese National Knowledge infrastructure (CNKI) for PEH was conducted to investigate the characteristics of the disease, 26 related articles were retrieved and 40 cases of PEH were reported. According to available literature, the average age at presentation is 51.8 years and the disease occurred more often in men than women. The etiology of the disease remained unknown. Chest pain, cough, and dyspnea were the common symptoms. Computed tomography usually revealed pleural effusion and pleural thickening. Histological examinations revealed mainly epithelioid cells. Immunohistochemical stains were positive for vascular endothelial markers. PEH tends to have more aggressive behavior than tumors in other locations, thus effective treatment has not yet been established until now. Further studies are needed to analyze the prognostic factors, clinical features and treatment of PEH.

Spontaneous bilateral haemothorax as presentation of primary pleural epithelioid haemangioendothelioma

Pleural epithelioid haemangioendothelioma (EHE) is a rare tumour that originates in the vascular endothelium with an intermediate degree of malignancy between haemangioma and angiosarcoma. Smoking and asbestos exposure are unproven risk factors and diagnosis is usually confirmed by thoracoscopy, since pleural fluid (PF) cytology is often not conclusive. Immunohistochemistry can also help to confirm the diagnosis. We report an 85-year-old patient with bilateral pleural EHE diagnosed by thoracoscopy, who debuted with a spontaneous bilateral haemothorax, the second described so far, and we conducted a thorough review of the literature to describe the clinical, radiological and prognostic features, as well as the PF, of this rare tumour.

Immunoreactivity for calretinin and keratins in desmoid fibromatosis and other myofibroblastic tumors: a diagnostic pitfall

Calretinin is an intracellular calcium-binding EF-hand protein of the calmodulin superfamily. It plays a role in diverse cellular functions, including message targeting and intracellular calcium signaling. It is expressed in the mesothelium, mast cells, some neural cells, and fat cells, among others. Because of its relative specificity for mesothelial neoplasms, calretinin is widely used as one of the primary immunohistochemical markers for malignant mesothelioma and in differentiating it from adenocarcinoma. On the basis of our sporadic observation on calretinin immunoreactivity in desmoid fibromatosis, we systematically evaluated calretinin, keratin cocktail (AE1/AE3), and WT1 immunoreactivity in 268 fibroblastic/myofibroblastic neoplasms. Calretinin was observed in 75% (44/58) of desmoid fibromatosis, 50% (21/42) of proliferative fasciitis, 23% (8/35) of nodular fasciitis, 33% (13/40) of benign fibrous histiocytoma, 35% (22/62) of malignant fibrous histiocytoma, and 13% (4/31) of solitary fibrous tumors but not in normal connective tissue fibroblasts at various sites. Keratin AE1/AE3 immunoreactivity was also commonly (6/13) present in the large ganglion-like cells of proliferative fasciitis and sometimes in nodular fasciitis (3/35), solitary fibrous tumor (3/27), and malignant fibrous histiocytoma (9/62). Nuclear immunoreactivity for WT1 or keratin 5 positivity was not detected in myofibroblastic tumors. On the basis of these observations, it can be concluded that calretinin and focal keratin immunoreactivity is fairly common in benign and malignant fibroblastic and myofibroblastic lesions. Calretinin-positive and keratin-positive spindle cells in desmoid and nodular fasciitis or calretinin-positive ganglion-like cells in proliferative fasciitis should not be confused with elements of epithelioid or sarcomatoid mesothelioma. These diagnostic pitfalls can be avoided with careful observation of morphology, quantitative differences in keratin expression, and use of additional immunohistochemical markers such keratin 5 and WT1 to verify true epithelial and mesothelial differentiation typical of mesothelioma.

Molecular changes in mesothelioma with an impact on prognosis and treatment

CONTEXT

In recent decades, research on malignant pleural mesothelioma (MPM) has been developed to improve patients' outcomes by increasing the level of confidence in MPM diagnosis and prognosis.

OBJECTIVE

To summarize data on genetic and epigenetic abnormalities in MPM that may be of interest for a better management of patients with MPM.

DATA SOURCES

Data were obtained from scientific publications on genetic and epigenetic abnormalities in MPM by studying gene mutations, DNA methylation, and gene and microRNA expression profiling.

CONCLUSIONS

Molecular changes in MPM consist in altered expression and in activation or inactivation of critical genes in oncogenesis, especially tumor suppressor genes at the INK4 and NF2 loci. Activation of membrane receptor tyrosine kinases and deregulation of signaling pathways related to differentiation, survival, proliferation, apoptosis, cell cycle control, metabolism, migration, and invasion have been demonstrated. Alterations that could be targeted at a global level (methylation) have been recently reported. Experimental research has succeeded especially in abolishing proliferation and triggering apoptosis in MPM cells. So far, targeted clinical approaches focusing on receptor tyrosine kinases have had limited success. Molecular analyses of series of MPM cases have shown that defined alterations are present in MPM subsets, consistent with interindividual variations of molecular alterations, and suggesting that identification of patient subgroups will be essential to develop more specific therapies.

Primary pleural leiomyosarcoma with rapid progression and fatal outcome: a case report

Introduction

Leiomyosarcomas are neoplasms of smooth muscles that most commonly arise from the uterus, gastrointestinal tract, or soft tissue. Primary pleural leiomyosarcoma is extremely rare. To the best of our knowledge, only nine cases have been published to date. Because of the rarity of pleural leiomyosarcoma and its similarity (clinical and histological) to other pleural neoplasms, particularly sarcomatous mesothelioma, diagnosis is often difficult.

Case presentation

A 58-year-old North African man was admitted with complaints of dyspnea and chest pain to our hospital. Chest computed tomography revealed right pleural effusion and pleural thickening. A transthoracic needle biopsy yielded a diagnosis of leiomyosarcoma, and tumor cells were strongly and uniformly positive for vimentin, a smooth muscle actin at immunohistochemical analysis. A general examination did not show any metastatic lesions in other areas. One month after diagnosis, the tumor grew rapidly, with pulmonary invasion, and therefore he was treated only by palliative care. He died from respiratory failure one month later. Because no organ of origin of the leiomyosarcoma, other than the pleura, was detected, this case was diagnosed as a primary pleural leiomyosarcoma.

Conclusions

Although leiomyosarcoma originating from the pleura is rare, this entity is increasingly described. The purpose of presenting this case report is to raise awareness among clinicians to consider this clinical entity as a differential diagnosis when a pleural mass is identified.

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.

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.

Value of immunohistochemistry in the differential diagnosis of pleural sarcomatoid mesothelioma from lung sarcomatoid carcinoma

AIMS

The differential diagnosis of pleural sarcomatoid mesothelioma (SM) from lung sarcomatoid carcinoma (LSC) invading parietal pleura and chest wall is a challenging issue. The aim of this study was to identify useful antibodies that can be used for the differential diagnosis of pleural SM from LSC.

METHODS AND RESULTS

Forty-five cases of pleural SM and 27 cases of LSC were immunohistochemically analysed by using 15 commercially available antibodies, including D2-40 and antibodies to calretinin, thrombomodulin, Wilms' Tumour 1, carcinoembryonic antigen (CEA), Napsin A, thyroid transcription factor (TTF)-1, pan-cytokeratin, CAM5.2, epithelial membrane antigen, Ber-EP4, MOC-31, alpha-smooth muscle actin, h-caldesmon and desmin. The results revealed that D2-40 positivity was significantly higher in pleural SM (86.7%) than in LSC (25.9%). The positivity of the adenocarcinoma markers, including CEA, Napsin A, and TTF-1, was low even in LSC.

CONCLUSIONS

Evaluating the positivity and degree of staining of the well-known mesothelial marker D2-40 could be applied to differentiate pleural SM from the sarcomatoid component of LSC, in addition to assessing clinical and radiological information.

Review article: pulmonary sarcomatoid carcinomas: a practical overview

Pulmonary sarcomatoid carcinomas (PSCs) are currently defined as poorly differentiated non-small-cell carcinomas containing a component with sarcoma or sarcoma-like (spindle and/or giant cell) features. They consist of 5 major histological variants, namely pleomorphic carcinoma, spindle cell carcinoma, giant cell carcinoma, carcinosarcoma, and pulmonary blastoma. The segregation of PSCs into a distinct clinicopathologic entity seems justified on the basis of morphologic, behavioral, and genotypic/phenotypic attributes. As a group, PSCs generally run an aggressive clinical course and may cause major difficulties in the differential diagnosis with other primary and secondary malignancies of the lung. At present, PSCs are believed to represent a family of carcinomas "in transition," in which diverse pathways of clonal evolution account for histological differences of a common ancestor lesion. The sarcomatous or sarcomatoid component of these tumors is thought to derive from carcinoma cells during the progression of carcinogenesis through the activation of an epithelial-mesenchymal transition program leading to sarcomatous transformation or metaplasia (conversion paradigm). Conceivably, targeting the epithelial-mesenchymal transition program could become a valid therapeutic strategy for these life-threatening tumors, whose sensitivity to current medical manipulation is disappointing.

Malignant mesothelioma with heterologous elements: clinicopathological correlation of 27 cases and literature review

Only a small number of malignant mesotheliomas with heterologous elements have been described. There are currently no criteria for diagnosis and little data regarding prognosis. We suggest that the term heterologous mesothelioma should be reserved for tumours that show malignant heterologous elements, notably osteosarcomatous, chondrosarcomatous, or rhabdomyoblastic elements but have immunohistochemical and clinical characteristics of mesothelioma. We identified 27 such cases and characterized the clinical and pathological characteristics of these tumours. In our series, 89% originated in the pleura, and 11% from the peritoneal cavity. The median age at diagnosis was 68 years, ranging from 27 to 85 years. Of these cases, 93% occurred in males and 7% in women. Of the 27 mesothelioma cases 16 (59%) were sarcomatoid, 10 (37%) were biphasic, and one was reported as epithelioid; 40% (11 cases) showed osteosarcomatous elements only, 19% showed areas of rhabdomyosarcoma only, 19% contained areas of chondrosarcoma only, and 22% exhibited osteochondromatous elements. Immunohistochemical labelling for cytokeratins was present in the majority of cases. Exposure to asbestos was identified in all the 17 cases for which an exposure history was available (63%). Median survival was 6 months after diagnosis, similar to the survival seen in sarcomatoid mesotheliomas. The differential diagnosis includes primary and secondary pleural sarcomas, including osteosarcomas and chondrosarcomas. Immunohistochemical labelling for cytokeratins is helpful in the distinction, but lack of labelling for cytokeratins in a spindle cell/sarcomatoid tumour does not exclude the diagnosis of mesothelioma, irrespective of the presence of heterologous elements. We suggest that if the anatomical distribution conforms to that of mesothelioma, a diagnosis of heterologous mesothelioma should be made in preference to a diagnosis of primary pleural osteosarcoma or chondrosarcoma, regardless of cytokeratin positivity, as for conventional non-heterologous sarcomatoid mesothelioma.

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.

Establishment and characterization of two distinct malignant mesothelioma cell lines with common clonal origin

We describe two newly established malignant mesothelioma (MM) cell lines derived from a pleural effusion of a male. One cell line, designated as MM-Z03E, reveals an epithelioid cobblestone morphology, while the second one, designated as MM-Z03S and subcloned after in vivo selection, exhibits a sarcomatoid storiform growth pattern. Both cell lines showed the immunologic profile characteristic for MM (i.e., expression of cytokeratin, CK18, calretinin, and vimentin in both phenotypes). Cytogenetics, multicolor fluorescence in situ hybridization, comparative genomic hybridization, and oligonucleotide array CGH were performed on both cell lines. Aberrations shared by both cell lines included chromosomal losses of 1q34 approximately qter, 4, 9p, 10p, 13, 14, 16q, 18, and 22, as well as a complex structural aberration involving chromosome 17. Aberrations exclusive to MM-Z03E included gains of 3q11q27 and 5p, while gain of 9q and losses of 3q27qter, 11q, and 18 in MM-Z03S were exclusive to MM-Z03E. Both cell lines were able to develop solid transplant tumors in nude mice within 16 weeks, and immunophenotyping of tumor xenografts revealed an overall retained expression profile of the markers used. Remarkably, one xenograft from MM-Z03E revealed overexpression of p53 and widely invasive growth. In conclusion, both cell lines are useful in vivo and in vitro model systems to study the underlying genetic mechanisms of biphasic differentiation in MM, which can be of certain value considering the increasing relevance of assessing MM tumor biology for the clinical management of this disease.

Genomic profiling of malignant pleural mesothelioma with array-based comparative genomic hybridization shows frequent non-random chromosomal alteration regions including JUN amplification on 1p32

Genome-wide array-based comparative genomic hybridization analysis of malignant pleural mesotheliomas (MPM) was carried out to identify regions that display DNA copy number alterations. Seventeen primary tumors and nine cell lines derived from 22 individuals were studied, some of them originating from the same patients. Regions of genomic aberrations observed in >20% of individuals were 1q, 5p, 7p, 8q24 and 20p with gains, and 1p36.33, 1p36.1, 1p21.3, 3p21.3, 4q22, 4q34-qter, 6q25, 9p21.3, 10p, 13q33.2, 14q32.13, 18q and 22q with losses. Two regions at 1p32.1 and 11q22 showed a high copy gain. The 1p32.1 region contained a protooncogene, JUN, and we further demonstrated overexpression of JUN with real-time polymerase chain reaction analysis. As MPM cell lines did not overexpress JUN, our findings suggested that induction of JUN expression was involved in the development of MPM cells in vivo, which also might result in gene amplification in a subset of MPM. Meanwhile, the most frequent alteration was the 9p21.3 deletion, which includes the p16(INK4a)/p14(ARF) locus. With polymerase chain reaction analysis, we determined the extent of the homozygous deletion regions of the p16(INK4a)/p14(ARF) locus in MPM cell lines, which indicated that the deletion regions varied among cell lines. Our results with array comparative genomic hybridization analysis provide new insights into the genetic background of MPM, and also give some clues to develop a new molecular target therapy for MPM.

Gene expression profiles in asbestos-exposed epithelial and mesothelial lung cell lines

BACKGROUND

Asbestos has been shown to cause chromosomal damage and DNA aberrations. Exposure to asbestos causes many lung diseases e.g. asbestosis, malignant mesothelioma, and lung cancer, but the disease-related processes are still largely unknown. We exposed the human cell lines A549, Beas-2B and Met5A to crocidolite asbestos and determined time-dependent gene expression profiles by using Affymetrix arrays. The hybridization data was analyzed by using an algorithm specifically designed for clustering of short time series expression data. A canonical correlation analysis was applied to identify correlations between the cell lines, and a Gene Ontology analysis method for the identification of enriched, differentially expressed biological processes.

RESULTS

We recognized a large number of previously known as well as new potential asbestos-associated genes and biological processes, and identified chromosomal regions enriched with genes potentially contributing to common responses to asbestos in these cell lines. These include genes such as the thioredoxin domain containing gene (TXNDC) and the potential tumor suppressor, BCL2/adenovirus E1B 19kD-interacting protein gene (BNIP3L), GO-terms such as "positive regulation of I-kappaB kinase/NF-kappaB cascade" and "positive regulation of transcription, DNA-dependent", and chromosomal regions such as 2p22, 9p13, and 14q21. We present the complete data sets as Additional files.

CONCLUSION

This study identifies several interesting targets for further investigation in relation to asbestos-associated diseases.

D2-40 and calretinin - a tissue microarray analysis of 341 malignant mesotheliomas with emphasis on sarcomatoid differentiation

Anti-calretinin antibodies are useful to differentiate adenocarcinomas from malignant mesotheliomas of the lung. Therefore, calretinin expression is rarely reported for sarcomatoid mesotheliomas. Anti-podoplanin antibodies (eg D2-40) react with lymphatic endothelia, Kaposi's sarcoma, lymphangioma and mesotheliomas. For the interpretation of spindle cell lesions of the pleura, knowledge of calretinin and D2-40 expression frequencies in sarcomatoid mesothelioma is desirable. To systematically investigate the sensitivity of calretinin and D2-40 antibodies in epithelioid and sarcomatoid areas of malignant mesotheliomas, a tissue microarray with 341 malignant mesotheliomas, including 112 epithelioid, 46 sarcomatoid and 183 biphasic tumors was constructed. Epithelioid and sarcomatoid differentiated tumor areas were clearly separated within the tissue microarray. Expression of calretinin and D2-40 was separately studied in epithelioid and sarcomatoid areas by immunohistochemistry. Calretinin expression was found in 91% of epithelioid and 57% of sarcomatoid tumor areas. D2-40 immunostaining was present in 66% of the epithelioid and 30% of the sarcomatoid tumor areas. A combination of calretinin and D2-40 increased the sensitivity in epithelioid tumor areas to 0.96 and in sarcomatoid tumor areas to 0.66. These data indicate that a combination of calretinin and D2-40 will improve diagnostic accuracy for spindle cell lesions of the pleura, whereas almost all epithelioid mesotheliomas are identified by calretinin alone.

Cytogenetic and molecular genetic changes in malignant mesothelioma

Malignant mesothelioma (MM) results from the accumulation of a number of acquired genetic events, especially deletions, which lead to the inactivation of multiple onco-suppressor genes in a multistep cascade mechanism. Past asbestos exposure represents the major risk factor for MM, and the link between asbestos fibers and MM has been largely proved by several epidemiologic and experimental studies. Asbestos fibers induce DNA and chromosomal damage. Most MM cases have shown multiple chromosomal abnormalities. Chromosomal losses are more common than gains. The most common cytogenetic abnormality in MM is a deletion in 9p21, the locus of CDKN2A, a tumor suppressor gene (TSG). The deletion of CDKN2A is a negative prognostic factor in MM. Loss of TSG CDKN2A/p14(ARF) is also common in MM and mutations in NF2 occur in approximately half of the cases. Despite the ban on asbestos use in Western countries, the incidence of MM is increasing, and asbestos is still used in developing countries. This epidemiologic situation calls for further research. Ongoing studies are already applying high-throughput genomic profiling methods in MM. Genetic alterations observed in MM may be useful in differential diagnosis between lung cancer and MM, as diagnostic markers or therapeutic targets, and as indicators of premalignancy for primary prevention and health surveillance.

Epithelioid and sarcomatoid malignant pleural mesothelioma in endoscopic gastric biopsies: a diagnostic pitfall

Pleural malignant mesothelioma (MM) usually presents with chest pain, pleural effusion, or cough in middle-aged and elderly individuals with a history of asbestos exposure, but may rarely present at unusual metastatic sites. The luminal gastrointestinal (GI) tract is only rarely involved in patients with wide-spread disease at autopsy. Encountering MM in endoscopic GI biopsies is an exceptionally rare event in surgical pathology practice and may therefore pose great diagnostic challenges if not considered, in particular if the clinical history is not informative or the GI symptoms are the presenting signs of the disease. To our knowledge, only three cases of epithelioid mesothelioma (EM) involving the luminal GI tract (intestine) have been reported so far, but no case of sarcomatoid MM (SM) involving the GI mucosa has been described. We herein present the first two cases of MM (one each of EM and SM) of the pleura, presenting in endoscopic gastric biopsies as small polypoid lesions and poorly healing ulcers 30 and 35 months after the initial diagnosis of pleural MM, respectively. The major differential diagnoses encompass primary or metastatic adenocarcinoma in case one and cytokeratin-positive (KIT negative!) GI stromal tumors (GISTs) and sarcomatoid carcinoma in case two, as well as other rare entities.