Molecular and Immunohistochemical Testing in Mesothelioma and Other Mesothelial Lesions.

CONTEXT.­: Molecular testing has increasingly been utilized in the evaluation of mesothelioma. Diffuse mesothelioma comprises multiple distinct genetic subgroups. While most diffuse mesotheliomas lack oncogenic kinase mutations and instead harbor alterations involving tumor suppressors and chromatin regulators, a minor subset of tumors is characterized by uncommon alterations such as germline mutations, genomic near-haploidization, ALK rearrangement, ATF1 rearrangement, or EWSR1::YY1 fusion. OBJECTIVE.­: To provide updates on the salient molecular features of diffuse mesothelioma, mesothelioma in situ, and other mesothelial lesions: well-differentiated papillary mesothelial tumor, adenomatoid tumor, peritoneal inclusion cyst, and others. We consider the diagnostic, prognostic, and predictive utility of molecular testing in mesothelial lesions. DATA SOURCES.­: We performed a literature review of recently described genetic features, molecular approaches, and immunohistochemical tools, including BAP1, MTAP, and merlin in mesothelioma and other mesothelial lesions. CONCLUSIONS.­: Our evolving understanding of the molecular diversity of diffuse mesothelioma and other mesothelial lesions has led to considerable changes in pathology diagnostic practice, including the application of immunohistochemical markers such as BAP1, MTAP, and merlin (NF2), which are surrogates of mutation status. In young patients and/or those without significant asbestos exposure, unusual mesothelioma genetics such as germline mutations, ALK rearrangement, and ATF1 rearrangement should be considered.

Review of the impact of the International System for Serous Fluid Cytopathology.

The International System for Reporting Serous Fluid Cytology (TIS) has been proposed by an expert working team composed of the International Academy of Cytology and the American Society of Cytopathology, following an international survey. Since its introduction, the TIS has gained worldwide acceptance, and this review aims to assess its global impact. A literature search revealed 25 studies which have presented data on the impact of the TIS. Most of them provide data, including risk of malignancy (ROM) for each diagnostic category, separately for pleural, peritoneal and pericardial effusions, while a few do not separate them. A few studies focus on specific diagnoses like mesothelioma on specific types of fluids or more specific issues like the optimal fluid volume for cytology or interobserver variability. A synopsis of the data from the literature search is presented in four tables. The ROM assessment is discussed, as well as interobserver variability and the use of ancillary diagnostic immunochemistry. In conclusion, our review of the published data suggests that the TIS is a valid classification scheme that has been widely accepted by pathologists globally, is highly reproducible and makes a valuable contribution to clinical therapeutic management.

Solid papillary mesothelial tumor.

We report nine examples of a previously undescribed type of peritoneal circumscribed nodular mesothelial tumor characterized by nests or sheets of mesothelial cells with sharp cell borders and extremely bland, sometimes grooved, nuclei. In some cases, nests were separated by fibrous bands. All patients were women, age range 30-72 years (median 52 years). All tumors were incidental findings during surgery and grossly were either solitary nodules or a few small nodules on the peritoneal surface. Referring pathologic diagnoses included diffuse malignant mesothelioma, localized malignant mesothelioma, well-differentiated papillary mesothelioma, and adenomatoid tumor. No tumor showed BAP1 loss by immunohistochemistry nor deletion of CDKN2A by FISH. RNA-seq revealed that these tumors clustered together and were distinct from peritoneal diffuse malignant mesotheliomas. Very few mutations or translocations were found, none of them recurrent from tumor to tumor, and no tumor showed an abnormality in any of the genes typically mutated/deleted in diffuse malignant mesothelioma. Array CGH on three cases revealed two with a completely flat profile and one with a small deletion at 3q26-3q28. On follow-up (range 5-60, median 34 months), there were no deaths, no recurrences, and no evidence of metastatic disease nor local spread; one case that initially had scattered nodules on the pelvic peritoneum had the same pattern of nodules at a second look operation 2 years later. We propose the name solid papillary mesothelial tumor for these lesions. These appear to be either benign or very low-grade tumors that need to be separated from malignant mesotheliomas.

Patient-derived and artificial ascites have minor effects on MeT-5A mesothelial cells and do not facilitate ovarian cancer cell adhesion.

The presence of ascites in the peritoneal cavity leads to morphological and functional changes of the peritoneal mesothelial cell layer. Cells loose cell-cell interactions, rearrange their cytoskeleton, activate the production of fibronectin, and change their cell surface morphology in a proinflammatory environment. Moreover, ovarian cancer cell adhesion has been shown to be facilitated by these changes due to increased integrin- and CD44-mediated binding sites. In this study, the biological responsiveness of the human pleural mesothelial cell line MeT-5A to patient-derived and artificial ascites was studied in vitro and adhesion of ovarian cancer cells, i.e. SKOV-3 cells, investigated. Changes were mainly observed in cells exposed to artificial ascites containing higher cytokine concentrations than patient-derived ascites. Interestingly, reduced cell-cell interactions were already observed in untreated MeT-5A cells and effects on tight junction protein expression and permeability upon exposure to ascites were minor. Ascites induced upregulation of CDC42 effector protein 2 expression, which affects stress fiber formation, however significant F-actin reorganization was not observed. Moreover, fibronectin production remained unchanged. Analysis of mesothelial cell surface characteristics showed upregulated expression of intercellular adhesion molecule 1, slightly increased hyaluronic acid secretion and decreased microvillus expression upon exposure to ascites. Nevertheless, the observed changes were not sufficient to facilitate adhesion of SKOV-3 cells on MeT-5A cell layer. This study revealed that MeT-5A cells show a reduced biological responsiveness to the presence of ascites, in contrast to published studies on primary human peritoneal mesothelial cells.

Emperipolesis of lymphocytes by mesothelial cells in pleural effusion involved by T-lymphoblastic lymphoma.

Emperipolesis is a physiologic or pathologic phenomenon characterized by the presence of intact viable cells within the cytoplasm of another cell. It has been described in normal tissues and in a variety of inflammatory and neoplastic lesions such as Rosai-Dorfman disease, tumors, hematopoietic disorders and rarely lymphomas. Emperipolesis by mesothelial cells is rare. Few cases of mesothelial emperipolesis of neoplastic lymphocytes in pleural effusions involved by lymphomas have been reported in the literature. Its etiopathogenesis and significance are controversial and speculative. We report a case of a 36-year-old man who presented with cough, chest pain, breathing difficulty, pericardial, and bilateral pleural effusions secondary to mediastinal T-lymphoblastic lymphoma. Pleural fluid cytology slides and cell block sections showed numerous single dispersed neoplastic lymphoblasts with occasional giant multinucleated mesothelial cells with emperipolesis of lymphocytes. The background showed scattered and clumped apoptotic karyorrhexis debris and reactive mesothelial cells. Cell block immunohistochemistry showed CD3, CD5, CD7, CD10, CD99, and TdT positive lymphocytes, consistent with involvement by T-lymphoblastic lymphoma. The giant cells were positive for cytokeratin, calretinin and WT1 confirming their mesothelial origin. Lymphoid effusions with emperipolesis may raise a potential diagnostic pitfall because they may morphologically be confused with other inflammatory and neoplastic lesions. This cell-in-cell phenomenon can be a helpful clue in the differential diagnosis of lymphocyte-rich effusions since it has been described in association with lymphomas. It might shed some light on the lymphocyte-mesothelial interaction and the potential phagocytic antigen-presenting properties of mesothelial cells under certain circumstances.

The Morphological Analysis of Cells in the Peritoneal Washing Fluids of Patients with Gastric Cancer.

The cytology of peritoneal washing fluids for gastric cancer is the most basic method for judging peritoneal micrometastasis. However, the clinical value of this method is not clear at present. A retrospective analysis was performed on 277 patients with pathologically proven and surgically treated gastric cancer. The peritoneal washing fluids were collected after opening the abdomen and before the operation, and were sent to the cytology laboratory for screening of occult cancer cells in the collected washing fluids. The number of cases diagnosed as cancer cells, reactive mesothelial cells, serosal balls, and traumatic mesothelial cells were 42, 18, 27, and 190, respectively. Typical adenocarcinoma cell nests were found in eight of 10 T4b samples, whereas 34 cases of cancer cells in T3 and T4a showed that these cell nests usually contained mesothelial cells, and the three-dimensional stereoscopic sense of the nests was not obvious. In the specific subcellular morphological changes of both reactive mesothelial cells and serosal balls, the changes of both the contour of nuclear membrane and the polarity of cell alignment were present only in stage T3 and T4a. The presence or absence of mesothelial cells in the nests of cancer cells and the changes of the contour of nuclear membrane and of the polarity of cell alignment in reactive mesothelial cells or serosal balls may help us to predict the depth of invasion of cancer cells.

Diagnostic value of BRCA1-associated protein-1, glucose transporter-1 and desmin expression in the discrimination between reactive mesothelial proliferation and malignant mesothelioma in tissues and effusions.

OBJECTIVE: The aim of this study was to investigate the utility of BRCA1-associated protein-1 (BAP1), glucose transporter (GLUT)-1 and desmin expression by immunohistochemistry in the discrimination between reactive and malignant mesothelial proliferations. METHODS: A total of 88 biopsies and 30 effusions from mesothelioma cases were studied. Control groups were composed of 35 tissues and 30 cell blocks. The 88 mesothelioma cases were from 43 males and 45 females (mean age 56 years). Tumours were mostly localised to pleura (66/88, 75%) and of epithelioid histology (75/88, 85%). Cytology samples were from 17 males and 13 females (mean age 58 years), and 16 pleural and 14 peritoneal effusions. Twenty cytology cases had corresponding tissue biopsies. RESULTS: BAP1 loss was detected in 61/88 (69%) tissues and in 20/30 (67%) cytology samples from mesothelioma with a specificity of 100% for both sampling methods. BAP1 loss was observed more frequently in pleural and biphasic tumours. GLUT-1 immunoreactivity was identified in 54/81 (67%) and 23/25 (92%) malignant tissues and effusions, and in 6/33 (18%) and 6/30 (20%) benign tissues and effusions, respectively. Desmin loss was observed in 74/80 (92%) malignant biopsy samples, 16/21 (76%) malignant effusions and 10/34 (29%) of benign tissues, but in none of the reactive effusions. Concordance rate of results between biopsy and cytology was as follows: BAP1 20/20 (100%); GLUT-1 13/18 (72%); and desmin 10/14 (71%). CONCLUSIONS: BAP1, GLUT-1 and desmin are useful markers in the discrimination between reactive and malignant mesothelial proliferations. BAP1 loss seems to be diagnostic for mesotheliomas both in biopsy and cytology samples.

Multiloculated mesothelial cyst presenting as a malignant mimic.

A 46-year-old woman was referred for a second opinion regarding an intra-abdominal mass discovered on imaging performed for abdominal pain and distension. The tumour appeared to involve the small bowel, left colon and mesentery and was initially thought to be consistent with an infiltrative tumour or loculated mucinous ascites. Due to the unusual appearance of the tumour and suspicion for an omental-based mass, a laparoscopic resection was recommended to the patient. Intraoperatively, the tumour was found to be a multiloculated, benign appearing, omental cyst without involvement of the bowel and was completely resected laparoscopically. Pathology demonstrated a multiloculated peritoneal mesothelial cyst.

Metachronous Uterine Endometrioid Adenocarcinoma and Peritoneal Mesothelioma in Lynch Syndrome: A Case Report.

Lynch syndrome is a hereditary disease with germline mutation in a DNA mismatch repair gene, most often presenting with colorectal and/or endometrial carcinomas; however, the spectrum of Lynch syndrome-associated tumors is expanding. In this article, we report a case of a primary peritoneal epithelioid mesothelioma that developed in a Lynch syndrome patient 10 months after diagnosis of uterine endometrioid adenocarcinoma. To our knowledge, this is the first reported case of a Lynch syndrome patient with metachronous uterine endometrioid adenocarcinoma and primary peritoneal mesothelioma.

Dual preventive benefits of iron elimination by desferal in asbestos-induced mesothelial carcinogenesis.

Asbestos-induced mesothelial carcinogenesis is currently a profound social issue due to its extremely long incubation period and high mortality rate. Therefore, procedures to prevent malignant mesothelioma in people already exposed to asbestos are important. In previous experiments, we established an asbestos-induced rat peritoneal mesothelioma model, which revealed that local iron overload is a major cause of pathogenesis and that the induced genetic alterations are similar to human counterparts. Furthermore, we showed that oral administration of deferasirox modified the histology from sarcomatoid to the more favorable epithelioid subtype. Here, we used i.p. administration of desferal to evaluate its effects on asbestos-induced peritoneal inflammation and iron deposition, as well as oxidative stress. Nitrilotriacetate was used to promote an iron-catalyzed Fenton reaction as a positive control. Desferal significantly decreased peritoneal fibrosis, iron deposition, and nuclear 8-hydroxy-2'-deoxyguanosine levels in mesothelial cells, whereas nitrilotriacetate significantly increased all of them. Desferal was more effective in rat peritoneal mesothelial cells to counteract asbestos-induced cytotoxicity than in murine macrophages (RAW264.7). Furthermore, rat sarcomatoid mesothelioma cells were more dependent on iron for proliferation than rat peritoneal mesothelial cells. Because inflammogenicity of a fiber is proportionally associated with subsequent mesothelial carcinogenesis, iron elimination from the mesothelial environment can confer dual merits for preventing asbestos-induced mesothelial carcinogenesis by suppressing inflammation and mesothelial proliferation simultaneously.

Benign mesothelial mesenteric cyst: case report and literature review.

A rare case of a benign mesothelial cyst arising from the mesentery of the descending colon is presented. A 73 year old female presented with an asymptomatic mesenteric cyst on CT scan. Colonoscopy revealed extrinsic compression of the descending colon. Surgical resection of the cyst necessitated partial colon resection due to the adherent nature of the cyst to the colon and its mesentery. The details of the case are presented as well as a brief review of the relevant literature.

Membrane-type I matrix metalloproteinase-dependent ectodomain shedding of mucin16/ CA-125 on ovarian cancer cells modulates adhesion and invasion of peritoneal mesothelium.

Mucin16 [MUC16/cancer antigen 125 (CA-125)], a high-molecular-weight glycoprotein expressed on the ovarian tumor cell surface, potentiates metastasis via selective binding to mesothelin on peritoneal mesothelial cells. Shed MUC16/CA-125 is detectable in sera from ovarian cancer patients. We investigated the potential role of membrane type 1 matrix metalloproteinase (MT1-MMP, MMP-14), a transmembrane collagenase highly expressed in ovarian cancer cells, in MUC16/CA-125 ectodomain shedding. An inverse correlation between MT1-MMP and MUC16 immunoreactivity was observed in human ovarian tumors and cells. Further, when MUC16-expressing OVCA433 cells were engineered to overexpress MT1-MMP, surface expression of MUC16/CA-125 was lost, whereas cells expressing the inactive E240A mutant retained surface MUC16/CA-125. As a functional consequence, decreased adhesion of cells expressing catalytically active MT1-MMP to three-dimensional meso-mimetic cultures and intact ex vivo peritoneal tissue explants was observed. Nevertheless, meso-mimetic invasion is enhanced in MT1-MMP-expressing cells. Together, these data support a model wherein acquisition of catalytically active MT1-MMP expression in ovarian cancer cells induces MUC16/CA-125 ectodomain shedding, reducing adhesion to meso-mimetic cultures and to intact peritoneal explants. However, proteolytic clearing of MUC16/CA-125, catalyzed by MT1-MMP, may then expose integrins for high-affinity cell binding to peritoneal tissues, thereby anchoring metastatic lesions for subsequent proliferation within the collagen-rich sub-mesothelial matrix.

Specific mesothelial signature marks the heterogeneity of mesenchymal stem cells from high-grade serous ovarian cancer.

Mesenchymal stem/stromal cells (MSCs) are the precursors of various cell types that compose both normal and cancer tissue microenvironments. In order to support the widely diversified parenchymal cells and tissue organization, MSCs are characterized by a large degree of heterogeneity, although available analyses of molecular and transcriptional data do not provide clear evidence. We have isolated MSCs from high-grade serous ovarian cancers (HG-SOCs) and various normal tissues (N-MSCs), demonstrated their normal genotype and analyzed their transcriptional activity with respect to the large comprehensive FANTOM5 sample dataset. Our integrative analysis conducted against the extensive panel of primary cells and tissues of the FANTOM5 project allowed us to mark the HG-SOC-MSCs CAGE-seq transcriptional heterogeneity and to identify a cell-type-specific transcriptional activity showing a significant relationship with primary mesothelial cells. Our analysis shows that MSCs isolated from different tissues are highly heterogeneous. The mesothelial-related gene signature identified in this study supports the hypothesis that HG-SOC-MSCs are bona fide representatives of the ovarian district. This finding indicates that HG-SOC-MSCs could actually derive from the coelomic mesothelium, suggesting that they might be linked to the epithelial tumor through common embryological precursors.

Role of malignant ascites on human mesothelial cells and their gene expression profiles.

BACKGROUND: Malignant ascites is often present at diagnostic in women with advanced ovarian cancer (OC) and its presence is associated with a worse outcome. Human peritoneal mesothelial cells (HPMCs) are key components of malignant ascites. Although the interplay between HPMCs and OC cells is believed to be critical for tumor progression, it has not been well characterized. The purpose of this study was to assess the effect of ascites on HPMCs and clarify the role of HPMCs in OC progression. METHODS: Human OC ascites and benign peritoneal fluids were assessed for their ability to stimulate HPMC proliferation. Conditioned medium from ascites- and benign fluid-stimulated HPMCs were compared for their ability to attenuate apoptosis induced by TNF-related apoptosis-inducing ligand (TRAIL). We conducted a comparative analysis of global expression changes in ascites-stimulated HPMCs using Agilent oligonucleotide microarrays. RESULTS: As compared to benign peritoneal fluids, malignant ascites stimulated the proliferation of HPMCs. TRAIL-induced apoptosis was attenuated in OC cells exposed to conditioned medium from ascites-stimulated HPMCs as compared to OC cells exposed to conditioned medium from benign fluid-stimulated HPMCs. A total of 649 genes were differentially expressed in ascites-stimulated HPMCs. Based on a ratio of more than 1.5-fold and a P < 0.05, 484 genes were up-regulated and 165 genes were down-regulated in ascites-exposed HPMCs. Stimulation of HPMCs with OC ascites resulted in differential expression of genes mainly associated with the regulation of cell growth and proliferation, cell death, cell cycle and cell assembly and organization, compared to benign peritoneal fluids. Top networks up-regulated by OC ascites included Akt and NF-κB survival pathways whereas vascular endothelial growth factor (VEGF) pathway was down-regulated. CONCLUSIONS: The results of this study not only provide evidence supporting the importance of the interplay between cancer cells and HPMCs but also define the role that the tumor environment plays in these interactions.

CD147 immunohistochemistry discriminates between reactive mesothelial cells and malignant mesothelioma.

Malignant mesothelioma (MM) is a rare form of cancer. Its histopathological diagnosis is very difficult, as it exhibits a number of different appearances that can be misinterpreted as metastatic invasion or atypical hyperplasia. Thus, there is an urgent need to identify adequate markers to distinguish between benign and malignant cells, allowing the implementation of appropriate therapies and, possibly, specific directed therapies. MM, like other tumors, show an increase in glucose uptake, due to high rates of glycolysis, inducing an intracellular overload of acids. In this context, monocarboxylate transporters (MCTs) emerge as important players, by mediating the transmembranar co-transport of lactate with a proton, thereby, regulating pH and allowing continuous glycolysis. Importantly, proper MCT expression and activity depend on its co-expression with a chaperone, CD147, which is associated with poor prognosis in cancer. Twenty-two samples including reactive mesothelial cells, MM, and atypical mesothelial hyperplasias were evaluated for immunoexpression of MCT1, MCT4, and CD147. Expression of these proteins was compared with GLUT1 as a new promising marker for MM. Although MCT isoforms were not differentially expressed in the two types of cytological specimens, CD147, as GLUT1, was almost exclusively expressed in MM. Both MCT1 and MCT4 are not able to discriminate between mesothelial reactive cells and mesothelial malignant cells, while CD147 was able to distinguish these two proliferations. If confirmed, besides being a good marker for identification of MM, CD147 may also be a target for therapeutical strategies in this rare type of tumor.

Transforming growth factor-ß-induced protein (TGFBI) suppresses mesothelioma progression through the Akt/mTOR pathway.

As an uncommon cancer, mesothelioma is very hard to treat with a low average survival rate owing to its usual late detection and being highly invasive. The link between asbestos exposure and the development of mesothelioma in humans is unequivocal. TGFBI, a secreted protein that is induced by transforming growth factor-ß in various human cell types, has been shown to be associated with tumorigenesis in various types of tumors. It has been demonstrated that TGFBI expression is markedly suppressed in asbestos-induced tumorigenic cells, while an ectopic expression of TGFBI significantly suppresses tumorigenicity and progression in human bronchial epithelial cells. In order to delineate a potential role of TGFBI in mediating the molecular events that occur in mesothelioma tumorigenesis, we generated stable TGFBI knockdown mutants from the mesothelium cell line Met-5A by using an shRNA approach, and secondly created ectopic TGFBI overexpression mutants from the mesothelioma cell line H28 in which TGFBI is absent. We observed that in the absence of TGFBI, the knockdown mesothelial and mesothelioma cell lines exhibited an elevated proliferation rate, enhanced plating efficiency, increased anchorage-independent growth, as well as an increased cellular protein synthesis rate as compared with their respective controls. Furthermore, cell cycle regulatory proteins c-myc/cyclin D1/phosphor-Rb were upregulated; a more active PI3K/Akt/mTOR signaling pathway was also detected in TGFBI-depleted cell lines. These findings suggest that TGFBI may repress mesothelioma tumorigenesis and progression via the PI3K/Akt signaling pathway.