Diagnosis of pleural malignant mesothelioma in life--a practical approach

Guidelines for Pathologic Diagnosis of Mesothelioma: 2023 Update of the Consensus Statement From the International Mesothelioma Interest Group

CONTEXT.—

Mesothelioma is an uncommon tumor that can be difficult to diagnose.

OBJECTIVE.—

To provide updated, practical guidelines for the pathologic diagnosis of mesothelioma.

DATA SOURCES.—

Pathologists involved in the International Mesothelioma Interest Group and others with expertise in mesothelioma contributed to this update. Reference material includes peer-reviewed publications and textbooks.

CONCLUSIONS.—

There was consensus opinion regarding guidelines for (1) histomorphologic diagnosis of mesothelial tumors, including distinction of epithelioid, biphasic, and sarcomatoid mesothelioma; recognition of morphologic variants and patterns; and recognition of common morphologic pitfalls; (2) molecular pathogenesis of mesothelioma; (3) application of immunohistochemical markers to establish mesothelial lineage and distinguish mesothelioma from common morphologic differentials; (4) application of ancillary studies to distinguish benign from malignant mesothelial proliferations, including BAP1 and MTAP immunostains; novel immunomarkers such as Merlin and p53; fluorescence in situ hybridization (FISH) for homozygous deletion of CDKN2A; and novel molecular assays; (5) practical recommendations for routine reporting of mesothelioma, including grading epithelioid mesothelioma and other prognostic parameters; (6) diagnosis of mesothelioma in situ; (7) cytologic diagnosis of mesothelioma, including use of immunostains and molecular assays; and (8) features of nonmalignant peritoneal mesothelial lesions.

The cytologic diagnosis of mesothelioma: are we there yet?

INTRODUCTION

Mesothelioma is a rare but highly aggressive malignancy with poor prognosis that frequently present with recurrent effusions. Establishing the diagnosis by cytology can lead to early diagnosis and treatment and consequently improve prognosis.

MATERIALS AND METHODS

This review examines the cytological diagnosis of mesothelioma in the context of its historical and morphologic evolution and provides an update of the current reporting systems. Clues to identify the mesothelial and malignant nature of the sample are detailed as well as the supporting ancillary tests.

RESULTS

Cytologically, the samples are overwhelmingly cellular and malignancy is recognized by both architectural and cytological atypia. Numerous variably sized clusters and enlarged cells are easily identified, some with papillary architecture and collagen cores. Recognizing the mesothelial nature of the cells and supportive immunostains are essential to rule out the differential diagnosis of metastatic carcinomas and reactive mesothelium. Current ancillary tests such as homozygous deletion of CDKN2A, loss of BRCA1-associated protein, and methylthioadenosine phosphorylase expression can provide further support of malignancy.

CONCLUSIONS

At this time with the aid of current ancillary tests and in the hands of cytopathologists with adequate experience with the interpretation of effusions, the diagnosis of mesothelioma can be established with accuracy in most cases.

Mesothelioma

Mesothelioma arises from the surface serosal cells lining the pleural, peritoneal, and pericardial cavities. It has three variants including: epithelioid, sarcomatous/desmoplastic, and biphasic types. Mesothelioma cells, predominantly of the epithelioid type, can shed into effusions as sheets, clusters/ morulae, papillae, or single cells. The challenges to cytologic diagnosis of mesothelioma are two-fold: 1. distinguishing mesothelial cells from metastatic malignant (most commonly carcinoma) cells; 2. distinguishing reactive mesothelial from mesothelioma cells. Immunocytochemistry is a helpful aid to cytologic evaluation for the former. The distinction of reactive mesothelial cells from mesothelioma can be more difficult, as there is considerable overlap in their appearances in effusion specimens. Recently developed ancillary molecular and genetic tests are proving to be useful in confirming the diagnosis of malignant mesothelioma in cytology specimens.

Malignant Pleural Effusions

Malignant pleural effusions have a significant burden on patients and the health care system. Diagnosis is typically via thoracentesis, although other times more invasive procedures are required. Management centers around relief of dyspnea and patient quality of life and can be done via serial thoracentesis, indwelling pleural catheter, or pleurodesis. This article focuses on the diagnosis and management of malignant pleural effusion.

Medical thoracoscopy in the diagnosis of pleural disease: a guide for the clinician

INTRODUCTION

Developing a feasible and accurate means of evaluating pleural pathology has been an ongoing effort for over 150 years. Pleural fluid cellular and biomarker analyses are simple ways of characterizing and uncovering pathologic entities of pleural disease. However, obtaining samples of pleural tissue has become increasingly important. In cases of suspected malignancy and certain infections histopathology, culture, and molecular testing are necessary to profile diseases more effectively. The pleura is sampled via several techniques including blind transthoracic biopsy, image-guided biopsy, and surgical thoracotomy. Given the heterogeneity of pleural disease, low diagnostic yields, or invasiveness no procedural gold standard has been established in pleural diagnostics.

AREAS COVERED

Herein, we provide a review of the literature on medical thoracoscopy (MT), its development, technical approach, indications, risks, current and future role in the evaluation of thoracic disease. Pubmed was searched for articles published on MT, awake thoracoscopy, and pleuroscopy with a focus on reviewing literature published in the past 5 years.

EXPERT OPINION

As the proficiency and number of interventional pulmonologists continues to grow, MT is ideally positioned to become a front-line diagnostic tool in pleural disease and play an increasingly prominent role in the treatment algorithm of various pleural pathologies.

Diagnostic value of ultrasound-guided needle biopsy in undiagnosed pleural effusions: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

Undiagnosed pleural effusions (UPEs) are a common problem of respiratory medicine, leading to an increased diagnostic burden globally. However, the most efficient and cost-effective approaches to UPEs remain controversial. This study aimed to assess the diagnostic value of ultrasound-guided needle biopsy (UGNB) in UPEs.

METHODS

We conducted a search of PubMed, Embase, the Cochrane Library and reference lists of retrieved studies with no publication data limitation. Articles that investigated the diagnostic accuracy of UGNB in UPEs were included. The quality of eligible studies was assessed using Quality Assessment of Diagnostic Accuracy Studies-2. The diagnostic value of UGNB was evaluated by calculating the pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds rate, and the area under the curve for the summary receiver operating characteristic curve using a random effects model.

RESULTS

Seven studies comprising 165 patients with UPEs met the inclusion criteria. UGNB had a pooled sensitivity of 83% (95% confidence intervals [CI], 75% - 89%), a specificity of 100% (95% CI, 90% - 100%), a positive likelihood ratio of 8.89 (95% CI, 3.29 - 24.02), a negative likelihood ratio of 0.23 (95% CI, 0.16 - 0.33), a diagnostic odds rate of 51.47 (95% CI, 14.70 - 180.16), and an area under the curve of 0.94. Six pneumothorax cases (3.6%), 5 local wound infections (3.0%), and 1 empyema case (less than 1%) were observed. There was no significant heterogeneity or publication bias in this study.

CONCLUSIONS

Based on current evidence, UGNB is a safe and convenient procedure with a high accuracy for diagnosing UPEs. However, physicians should still be cautious in interpreting negative UGNB results.

The Mesothelial Cells in CAPD Effluent and Their Relation to Peritonitis Incidence

The total cell count and cell differentiation of the overnight peritoneal dialysis effluent (PDE) was analysed in 34 long-term CAPD patients. The mean percentage and yield of mesothelial cells were 3.1% and 0.17 × 106 per PDE. There was a significant lower percentage and yield of mesothelial cells in the PDE of patients with a peritonitis incidence (PI) of more than 2 episodes a year. Independent of dwell time, a positive correlation between the total yield of leucocytes and the yield of mesothelial cells was found. No relation between the amount of phospholipids in the PDE and the yield of mesothelial cells could be shown. Mesothelial cells in the PDE are probably reflecting the turn-over rate of a reactive mesothelium. Whether a low turn-over rate of the mesothelium is causing or is caused by a high PI needs further investigation.

Advances in pleural diseases: what is the future for medical thoracoscopy?

PURPOSE OF REVIEW

Medical thoracoscopy provides the physician a window into the pleural space. The procedure allows biopsy of the parietal pleura under direct visualization with good accuracy. In addition, it achieves therapeutic goals of fluid drainage, guided chest tube placement, and pleurodesis.

RECENT FINDINGS

Comparable diagnostic yield is achieved with the flexi-rigid pleuroscope even though pleural biopsies are smaller using the flexible forceps as compared to rigid thoracoscopy. Flexi-rigid pleuroscopy is extremely well tolerated and can be performed safely as an outpatient procedure. Biopsy quality can be further enhanced with accessories that are compatible with the flex-rigid pleuroscope such as the insulated tip knife and cryoprobe.

SUMMARY

With more sensitive tools to image the pleura such as contrast-enhanced computed tomography, MRI, ultrasonography, PET, increased yield with image-guided biopsy as well as advances in cytopathology, what lies in the future for medical thoracoscopy remains to be seen. However, it is the authors' opinion that medical thoracoscopy will evolve with time, complement novel techniques, and continue to play a pivotal role in the evaluation of pleuropulmonary diseases.

Comparison of fibulin-3 and mesothelin as markers in malignant mesothelioma

BACKGROUND

Pleural malignant mesothelioma (MM) is a deadly tumour predominantly associated with asbestos exposure. A reliable diagnostic and prognostic marker for MM will significantly enhance clinical care and is an area of intense research. Soluble mesothelin is the most studied and an FDA-approved biomarker for MM. A recent report showed promising results using fibulin-3 as a new diagnostic marker. The aim of this study was to compare the utility of fibulin-3 versus mesothelin, singly or in combination.

METHODS

Fibulin-3 and soluble mesothelin were determined by ELISA in the plasma and pleural fluid of 153 patients presenting with a pleural effusion including 82 with MM, 36 with non-MM malignant effusions and 35 with benign effusions. Biomarker concentrations were determined in the plasma of an additional 49 cases with benign asbestos-related disease.

RESULTS

Mesothelin provides better diagnostic accuracy than fibulin-3 for MM whether measured in plasma or pleural effusion: area under the curve (AUC) for plasma was 0.822 (95% CI 0.76 to 0.87) compared with 0.671 (0.61 to 0.73), respectively, and for pleural fluid AUC was 0.815 (0.74 to 0.87) compared with 0.588 (0.51 to 0.67), respectively. Effusion fibulin-3 was an independent significant prognostic factor for survival in MM patients; HR 2.08 (1.14 to 3.82), p=0.017. MM patients with effusion fibulin-3 levels below the median survived significantly longer than those with levels above the median (14.1 vs 7.9 months, p=0.012). Mesothelin and neutrophil to lymphocyte ratio were not significant prognostic markers.

CONCLUSIONS

Soluble mesothelin is a superior diagnostic biomarker for MM compared with fibulin-3, whereas fibulin-3 provides superior prognostic information compared with mesothelin.

A diagnosis of malignant pleural mesothelioma can be made by effusion cytology: results of a 20 year audit

AIMS

Cytological diagnosis of malignant pleural mesothelioma (MPM) is controversial, but has been used in our institution for over 30 years. To assess the role of effusion cytology in mesothelioma diagnosis we conducted an audit of pleural fluid cytology results over a 20 year period (1988-2007).

METHODS

Pleural samples were received from 6285 patients; data linkage with Western Australian Cancer and Mesothelioma Registries demonstrated that 815 of these patients had a diagnosis of MPM. Cytological examination of a pleural effusion specimen had been performed in 517 (63%) of these 815 patients.

RESULTS

Definitive cytological diagnosis of MPM was made in 377/517 cases, resulting in an 'absolute' sensitivity of 73%. An additional 66 patients were diagnosed as atypical/suspicious, resulting in a 'complete' sensitivity of 86%. If only biopsy/necropsy proven cases are considered, the absolute sensitivity is 68% and the complete sensitivity is 82%. There were no false positive diagnoses of malignancy; two patients with metastatic adenocarcinoma were initially diagnosed as MPM, prior to the availability of specific mesothelial markers, resulting in a positive predictive value of 99%.

CONCLUSIONS

Effusion cytology is an inexpensive, minimally invasive procedure which should be included in the diagnostic work-up of cases of suspected MPM.

Sensitivity and specificity of immunohistochemical antibodies used to distinguish between benign and malignant pleural disease: a systematic review of published reports

AIMS

A systematic review of published reports that have evaluated the ability of immunohistochemistry and argyrophil nucleolar organizing region (AgNOR) staining to distinguish between benign and malignant pleural disease.

METHODS

Nineteen relevant papers published during the period 1979-2005 were identified. Individual results of immunohistochemistry for five diagnostic antibodies were extracted to calculate diagnostic sensitivity and specificity. results from five of these studies that had evaluated proliferation markers or AgNOR staining techniques were also summarized.

RESULTS

Most antibodies demonstrated poor to moderate diagnostic ability. Desmin and epithelial membrane antigen (EMA) were the most useful, with sensitivity and specificity both above 74%. The combination of EMA and AgNOR was reported as having 95% diagnostic sensitivity. A high MCM2 labelling index also differentiated between benign and malignant pleural disease.

CONCLUSIONS

Immunohistochemistry is of limited value, but newer diagnostic methods may be useful additions in this area of pathology. The diagnostic importance of histological features seen on plain tissue sections is emphasized as vital for correctly differentiating between benign pleural disease and malignant pleural mesothelioma.

Mesothelioma with non-pleural malignancy: a red herring or just an uncommon pairing?

Malignant pleural mesothelioma (MPM) is a highly aggressive cancer of the pleura with a well-established male predominance and causative link with asbestos exposure. We report four cases of female patients with MPM referred for palliation of symptoms thought to be due to previous non-pleural malignancy.With emerging novel treatments for MPM, this article discusses four unusual cases of MPM occurring in the setting of other malignancy, highlights the importance of considering a primary diagnosis of MPM even in patients with other malignancy, and reinforces the benefits of video-assisted surgical biopsy which allows simultaneous diagnosis and treatment.

Malignant mesothelioma

Malignant mesothelioma is an aggressive, treatment-resistant tumour, which is increasing in frequency throughout the world. Although the main risk factor is asbestos exposure, a virus, simian virus 40 (SV40), could have a role. Mesothelioma has an unusual molecular pathology with loss of tumour suppressor genes being the predominant pattern of lesions, especially the P16INK4A, and P14ARF, and NF2 genes, rather than the more common p53 and Rb tumour suppressor genes. Cytopathology of mesothelioma effusions or fine-needle aspirations are often sufficient to establish a diagnosis, but histopathology is also often required. Patients typically present with breathlessness and chest pain with pleural effusions. Median survival is now 12 months from diagnosis. Palliative chemotherapy is beneficial for mesothelioma patients with high performance status. The role of aggressive surgery remains controversial and growth factor receptor blockade is still unproven. Gene therapy and immunotherapy are used on an experimental basis only. Patterns identified from microarray studies could be useful for diagnosis as well as prognostication.

Malignant mesothelioma presenting as stroke - a case report

A case of a 64-year-old man with metastatic malignant mesothelioma is described in detail. When he presented to us he gave a history suggestive of transient ischaemic attack (TIA) 2 weeks before and 3 days after admission he developed weakness of the left upper limb. Computed tomographic scan of the brain revealed a solitary metastasis in the right cerebrum. A few days later, he developed subcutaneous metastasis in the chin. Malignant mesothelioma is considered to metastasize rarely and to spread locally. We suggest that distant metastasis in malignant mesothelioma is not uncommon and may be considered to behave like other forms of lung cancer. Treatment modalities should be studied in such patients.

Reactivity of six antibodies in effusions of mesothelioma, adenocarcinoma and mesotheliosis: stepwise logistic regression analysis

Anti-CEA, anti-vimentin, CAM5.2, BerEp4, Leu-M1 and anti-EMA were applied to effusions from 36 mesotheliomas, 53 adenocarcinomas and 24 reactive mesothelial proliferations. Stepwise logistic regression analysis selected three criteria of major importance for distinguishing between adenocarcinoma and mesothelioma: BerEp4, CEA and EMA accentuated at the cell membrane (mEMA), these three being of similar diagnostic value. The pattern BerEp4-, CEA- and mEMA+ was fully predictive for mesothelioma (sensitivity 47%), whereas the opposite pattern was fully predictive for adenocarcinoma (sensitivity 80%). Only EMA seemed to distinguish between mesotheliosis and mesothelioma. Comparison of reactivity in cytological and histological material from the same mesotheliomas showed similar staining frequencies for CEA and CAM5.2, with some random variation for Leu-M1 and EMA, whereas vimentin and BerEp4 reactivity was more frequent in cytological specimens.

The use of histological and immunohistochemical markers to distinguish pleural malignant mesothelioma and in situ mesothelioma from reactive mesothelial hyperplasia and reactive pleural fibrosis

Distinguishing malignant mesothelioma from reactive mesothelial hyperplasia and reactive fibrosis can be a diagnostic problem in small pleural biopsies, made more difficult by the recent recognition of mesothelioma-in-situ. Antibodies to epithelial membrane antigen (EMA), p53, and bcl-2 have all been advocated for differentiating reactive from neoplastic conditions, but reports are inconsistent. These antibodies have therefore been applied to 31 cases of malignant mesothelioma, 34 cases of reactive pleural disease (20 reactive mesothelial hyperplasia and 14 reactive pleural fibrosis) and four small biopsies that were initially coded as suspicious, from patients who later developed frank mesothelioma. Thirty out of 31 (97 per cent) cases of mesothelioma showed positive nuclear staining for p53, with a higher incidence of positivity in epithelioid than in sarcomatoid elements and 30/31 (97 per cent) showed diffuse linear membrane staining for EMA, again more intense in the epithelioid elements. No mesothelioma was positive for bcl-2. In seven cases that contained both in situ and invasive mesothelioma, the in situ elements showed similar staining patterns to the invasive epithelioid elements. Thirteen out of 20 (65 per cent) cases of reactive mesothelial hyperplasia showed occasional nuclear positivity for p53 and 5/20 (25 per cent) cases showed focal weak membrane staining for EMA. Three out of 14 (21 per cent) cases of reactive pleural fibrosis showed positive nuclear staining for p53 and 6/14 (43 per cent) cases showed focal membrane staining with EMA. No reactive cases stained for bcl-2. All four suspicious cases showed diffuse linear staining with EMA and three showed focal staining for p53. It is concluded that strong diffuse linear staining for EMA is a good marker of malignancy when differentiating epithelioid malignant mesothelioma and mesothelioma-in-situ from reactive mesothelial hyperplasia, although weak focal staining may occur in reactive conditions. Nuclear staining for p53 is also suggestive of epithelioid mesothelioma, but should be regarded as no more than suspicious. The antibodies used in this investigation are less helpful in differentiating sarcomatoid mesothelioma from reactive pleural fibrosis.

Cytologic diagnosis of malignant mesothelioma, with particular emphasis on the epithelial noncohesive cell type

The effusion cytologies from 21 cases of malignant mesothelioma (MM) (15 pleural, 6 peritoneal) diagnosed at the Indiana University Medical Center during 1990-1997 were reviewed. Using the classification of Tao (Acta Cytol 1979;23:209-213), 13 cases of MM were of the epithelial cohesive cell type and 8 were of the epithelial noncohesive cell type. While the epithelial cohesive cell type has been discussed in the literature, the epithelial noncohesive cell type has not. The cytomorphologic features for both types are presented with particular emphasis on the noncohesive cell type. The differential diagnosis and use of ancillary confirmatory laboratory tests are briefly discussed. Because of its resemblance to florid reactive mesothelial hyperplasia and the general lack of awareness of the existence of the single-cell pattern of mesothelioma, this diagnosis can often be missed.

Malignant mesothelioma of the pleura. The reproducibility of the immunohistological diagnosis

The reproducibility of the histopathological diagnosis of pleural malignant mesothelioma (MM), after supplementing routine H&E stain by immunohistochemistry (IH) in 77 cases of original diagnoses of MM, was assessed by examining interobserver variation between five pathologists. A battery of commercial antibodies (cytokeratins, vimentin, HMFG-2, anti Leu-M1 [CD15], BerEP4, B72.3 [TAG-72], carcinoembyonic antigen), considered to be useful in enhancing diagnostic accuracy, was used. The number of definitively classified tumors (accepted MM plus rejected MM) increased from 57 on H&E stain to 60 after IH, with 59 (76.6%) cases being accepted as true MM. Based on IH, the chance-adjusted interobserver agreement was poor (kappa w = 0.29) and lower than that observed on previous H&E alone. The intraobserver agreement for four of the five pathologists was rather good (kappa w = 0.54-0.56). The inter- and intraobserver concordance was higher in accepting than excluding the cases as MM. A larger number of cases were classified by all reviewers as mixed or sarcomatous variants after IH. In the interpretation of each immunostain, kappa values ranged from 0.19 for B72.3 to 0.62 for HMFG-2, which were respectively the least and the most consistently interpreted immunostains. The information additionally contributed by IH did not seem to change the pathologists' diagnoses very much in comparison with those made by routine H&E stain. Until highly specific and sensitive probes for the positive identification of MM become available, a careful scrutiny of routinely stained preparations still remains the most rewarding component of the diagnostic pathway.

The use of epithelial membrane antigen and silver-stained nucleolar organizer regions testing in the differential diagnosis of mesothelioma from benign reactive mesothelioses

BACKGROUND

The accurate diagnosis of pleural lesions obtained from small closed biopsy is difficult. As yet there is no single reliable test to distinguish between malignant and benign mesothelial tissue.

METHODS

Immunostaining of epithelial membrane antigen (EMA) and the quantitation of silver stained nucleolar organizer regions (AgNORs) each were applied to benign and malignant histologic sections of pleural and peritoneal biopsies. The usefulness of these stains was tested both individually and in combination in the diagnosis of epithelial malignant mesothelioma.

RESULTS

One hundred and three of the 141 malignant lesions (73%) were immunoreactive for EMA but only 3 of the 73 benign lesions (4%) reacted equivocally, and none positively. The average count of AgNORs/cell in malignant lesions (n = 80) was elevated compared with benign cases (n = 26), but a significant overlap was exhibited in the AgNOR count and this form of analysis was considered to be of little value in distinguishing benign from malignant mesothelial processes. Much less overlap was observed when the average AgNOR area was measured. By using the maximum benign AgNOR area of 0.6677 microm2 as the upper threshold, 51 cases (63.8%) were identified as malignant; the test demonstrated 100% specificity and 63.8% sensitivity. By combining the EMA and AgNOR results, 76 of 80 of the malignant mesothelioma cases (95%) tested positive for at least 1 of the tests with no false-positive results identified.

CONCLUSIONS

This study confirms the usefulness of EMA in diagnosing malignant and benign mesothelial lesions, and demonstrates the enhanced diagnostic value of combining EMA immunoreaction with the average area of AgNOR per cell, thereby increasing sensitivity in the diagnosis of epithelial malignant mesothelioma.

Newly marketed tissue markers for malignant mesothelioma: immunoreactivity of rabbit AMAD-2 antiserum compared with monoclonal antibody HBME-1 and a review of the literature on so-called antimesothelioma antibodies

A complementary DNA (cDNA) library was constructed from a human malignant mesothelioma (MM) cell line and a cDNA fragment encoding for a cytoplasmic mesothelial protein recognized by the polyclonal antibody AMAD-1 was then cloned and expressed in Escherichia coli. The purified recombinant protein was used to raise a novel antibody, named AMAD-2, in rabbits. This antibody reacted with normal mesothelium and most MM (15 of 17) on paraffin sections and featured a cytoplasmic labeling. Conversely, AMAD-2 immunostaining of normal and tumor tissues from body sites other than serosal membranes was limited with respect to the proportion of positive specimens and usually less conspicuous than in MM. AMAD-2 immunoreactivity was subsequently compared with staining for HBME-1, another newly marketed antimesothelial monoclonal antibody, concerning the ability to distinguish pleural MM from metastatic pleural tumors of epithelial type. A granular cytoplasmic immunoreactivity for AMAD-2 was present in 50% or more of tumor cells in all 84 MM, regardless of histological type, but also in 3 (7%) of 42 pleural metastases, albeit only focally. HBME-1 was shown in 63 of 66 epithelial MM and in the epithelial component of all 8 mixed MM, with a prevailingly membranous pattern, usually homogeneous and strong, whereas none of the 10 sarcomatous MM was positive. HBME-1 was also expressed in 6 (14%) of 42 pleural metastases in a cytoplasmic or membranous pattern. Compared with HBME-1, AMAD-2 showed a higher degree of specificity and sensitivity for MM. AMAD-2 still proved to be superior to HBME-1, also when sarcomatoid MM were excluded from the assessment. This finding supports the view that AMAD-2 is an antibody highly, although not entirely, specific for the mesothelial lineage, whereas HBME-1 is probably a cell marker more closely related to the epithelial differentiation of MM. Therefore, AMAD-2 is preferable as a positive tissue marker to be incorporated in the optimal immunohistochemical panel for the diagnosis of MM.

Complementary value of five carcinoma markers for the diagnosis of malignant mesothelioma, adenocarcinoma metastasis, and reactive mesothelium in serous effusions

Cytological slides of serous fluids of 41 malignant mesotheliomas, 88 metastatic adenocarcinomas, and 25 reactive effusions were immunostained with the antibodies anti-CEA, MOC-31, Leu-M1, Ber-EP4, and B72.3. Most mesotheliomas and all reactive fluids failed to stain with these antibodies. The sensitivity of the five markers to detect carcinoma cells differed remarkably. Especially MOC-31, Ber-EP4, and B72.3 stained with a high number of carcinoma cases and the complemetary value of Ber-EP4 and B72.3 to immunostain carcinoma cells was impressive: 94% of the metastatic adenocarcinoma cases reacted with Ber-EP4 or B72.3 in contrast to 1 of 41 malignant mesotheliomas.

Asbestos bodies in lung tissue following exposure to crocidolite

A series of 206 necropsies in Western Australia (WA) have had routine counts made of asbestos bodies in samples of lung tissue using conventional light microscopy. Thirty-two cases had worked in the asbestos industry at Wittenoom, WA and (log) counts of asbestos bodies in their lung tissue correlated well with estimates of their (log) cumulative airborne exposure to crocidolite fibers (r = 0.60). There was no association between the number of asbestos bodies and time since exposure to asbestos ceased. In subjects without known exposure to asbestos, there was a weak but nonsignificant increase in number of asbestos bodies with increasing age, with 26% of cases having no asbestos bodies present. It is concluded that the relatively simple technique of light microscopy for counting of asbestos bodies in lung tissue provides a reliable indication of the level of past occupational exposure to crocidolite in subjects whose exposure has been only to crocidolite. This could be extremely useful in follow-up studies of cohorts that lack reliable measures of airborne exposure to crocidolite asbestos.

Effects of asbestos and man-made vitreous fibers on cell division in cultured human mesothelial cells in comparison to rodent cells

We report the effects of chrysotile and crocidolite asbestos, and glass and rock wool fibers (man-made vitreous fibers, MMVF) on the induction of binucleate cells in vitro. The response of human mesothelial cells (target cells in fiber carcinogenesis) and rodent cells was compared. Human primary mesothelial cells, MeT-5A cells (an immortalized human mesothelial cell line), and rat liver epithelial (RLE) cells were exposed to asbestos and MMVF samples of similar size range. Milled glass wool, milled rock wool, and titanium dioxide were used as non-fibrous particle controls. All four fiber types caused statistically significant increases in the amount of binucleate cells in human primary mesothelial cells and MeT-5A cells (in the dose range 0.5-5.0 micrograms/cm2). Chrysotile and crocidolite asbestos were more effective (1.3-3.0-fold increases) than thin glass wool and thin rock wool fibers (1.3-2.2-fold increases). However, when the fiber doses were expressed as the number of fibers per culture area, the asbestos and MMVF appeared equally effective in human mesothelial cells. In RLE cells, chrysotile was the most potent inducer of binucleation (2.9-5.0-fold increases), but the response of the RLE cells to crocidolite, thin glass wool, and thin rock wool fibers was similar to the response of the human mesothelial cells. No statistically significant increases in the number of bi- or multinucleate cells were observed in human primary mesothelial cells or RLE cells exposed to the non-fibrous dusts. In MeT-5A cells exposed to 5 micrograms/cm2 of milled glass wool and milled rock wool, as well as in cultures exposed to 2 and 5 micrograms/cm2 of TiO2, significant increases were, however, observed. Our results show that rodent cells respond differently to mineral fibers than human cells. The results also add evidence to the suggested importance of disturbed cell division in fiber carcinogenesis.

Glycosaminoglycans from two human malignant mesothelioma cell lines: determination, distribution, and effect of platelet-derived growth factor on their synthesis

The synthesis and distribution of glycosaminoglycans (GAGs) were studied in two human malignant mesothelioma cell lines: one with fibroblast-like morphology and the other with epithelial differentiation. Analyses using highly sensitive high-pressure liquid chromatography techniques and agarose gel electrophoresis showed that these cells produce not only hyaluronan (HA) but also galactosaminoglycans (GalAGs, chondroitin sulfate and (or) dermatan sulfate) and heparan sulfate (HS). In both cell lines most of the HA (87-90%) and GalAGs (57-66%) are secreted into the extracellular matrix. Although HS is mainly bound to the cell surface in fibroblast-differentiated cells (75%), in epithelial type cells only 40% occurs in the cell-associated fraction. The amounts of secreted GAGs are 6- to 8-fold higher in epithelial than in fibroblast-like mesothelioma cultures. In cells with the fibroblast phenotype, the beta-homodimer of platelet-derived growth factor (PDGF) in a concentration of 1.5 ng/mL stimulates HA and GalAG synthesis 5-fold and that of HS 10-fold, whereas higher concentrations suppress this stimulatory effect. The stimulatory effect, observed at low concentrations of this growth factor, was completely blocked by the addition of antibodies against this factor. In epithelially differentiated cells, the production of all GAGs was suppressed after addition of this factor, even at low concentrations. We therefore suggest that mesothelioma cells can produce GAGs, the synthesis of which is dependent on the presence and concentration of PDGF beta-homodimer. The differences between the two cell lines regarding the effect of this growth factor on GAG synthesis indicates that the regulation of this synthesis is complex, other factors also being important.

Markers for metastatic adenocarcinoma in serous effusion specimens

A variety of stains have been proposed as useful adjuncts to the morphologic diagnosis of serous effusion specimens. This study evaluates the sensitivity and specificity of nine stains for the detection of metastatic adenocarcinoma in effusions. Mucin cytochemistry with the Periodic acid-Schiff reaction after diastase digestion (PASd) and the mucicarmine method, as well as immunochemical staining for five glycoprotein antigens, was undertaken on 153 effusion specimens with histological and/or clinically confirmed diagnoses. Immunochemical stains included three antibodies to CEA (Dako polyclonal, 4E7 and A5B7) and antibodies to HEA (Ber-EP4), TAG 72 (B72.3), CD15 (LeuM1) and Epithelial membrane antigen (EMA) were evaluated. The sensitivity of the stains for adenocarcinoma (102 cases) was: PASd 37%; mucicarmine 24%; polyclonal anti-CEA 69%; 4E7 52%; A5B7 21%; EMA 91%; B72.3 44%; Ber-EP4 32%; LeuM1 24%. With the exception of EMA, none of the stains reacted with any cases of benign mesothelial cells (11 cases), reactive mesothelial cells (34 cases), or with six cases of mesothelioma. However, EMA staining was present in two cases (6%) of reactive mesothelial cells and all cases of mesothelioma. The optimal combination of stains for use in a panel was polyclonal anti-CEA/B72.3/PASd. Combined results from these three stains yielded a sensitivity of 83% for adenocarcinoma with no false positive results. It is concluded that special staining may provide valuable information to assist in the classification of difficult effusion cases.

Mesothelioma-like tumors of the pleura: a review of 72 autopsy cases

The 72 mesothelioma-like tumors of the pleura (MLTP) found among 33 500 autopsy cases collected over more than 30 years are reviewed. MLTP have a worse prognosis than the 106 cases of pleural mesothelioma autopsied in our institutes with regard to survival time and metastatic spread. In MLTP, adenocarcinomas predominate with a wide range of histological and cytological variation and prominent development of connective tissue having its origin in the periphery of the lung. These intrapulmonary primary tumors often fulfill the criteria of pulmonary scar cancer. Etiologically, there is no correlation between the origin of this tumor and smoking or exposure to asbestos. The absence of mucus formation and glandular differentiation, together with the presence of spindle-shaped carcinoma components and strong mesothelial or stroma proliferation, can make the differential diagnosis between this tumor type and mesothelioma difficult. Immunohistological investigations were performed on 11 cases with antibodies against intermediate filament proteins, vascular endothelium, collagen IV, macrophage antigens, carcinoembryonic antigen (CEA), LeuM1, and the antibody BerEP4. Our investigation shows that a battery of several tumor markers, such as antibodies against LeuM1, CEA, and the antibody BerEP4, as well as staining with periodic acid/Schiff/diastase discriminate primary from secondary pleural neoplasms, whilst intermediate filament proteins alone are of little diagnostic value.

Thoracoscopy in pleural malignant mesothelioma: a prospective study of 188 consecutive patients. Part 1: Diagnosis

BACKGROUND

To compare the diagnostic value of thoracoscopic biopsy, fluid cytology, and Abrams needle biopsy, the authors analyzed prospectively the records of 188 patients with malignant pleural mesothelioma examined between 1973 and 1990. Symptoms were pleural effusion in 173 patients, empyema in 1, spontaneous pneumothorax in 1, and radiologic tumor without effusion in 13.

METHODS

Thoracoscopy was performed using a rigid thoracoscope under local anesthesia with neuroleptanalgesia. A total of 10-20 biopsies were taken from the parietal, diaphragmatic, and visceral pleura. Each diagnosis was confirmed by the French panel of mesothelioma pathologists. To prevent parietal seeding, radiation therapy at a dose of 21 Gy was administered during a period of 3 days to all points of entry.

RESULTS

Tolerance to thoracoscopy was good. The only complications were subcutaneous emphysema (1 patient), local pleural infection (4 patients), hemorrhage of less than 100 ml (3 patients), and temperature of 38-38.5 degrees C (26 patients). In 137 patients, the cavity was free, and complete endoscopic inspection was achieved. In 51 patients, inspection was limited by adhesions that were severed to obtain biopsy. Nonspecific inflammation was observed in 12 patients (6.5%), nodules in 92 (49%), thickening in 21 (11%), and mixed lesions in 63 (33.5%). Diagnosis was achieved by thoracoscopy in 98% of patients, by fluid cytology in 26%, and by needle biopsy in 21%.

CONCLUSION

In most patients, thoracoscopy allows complete visualization of the pleural cavity and provides high-quality biopsy samples. The diagnostic accuracy of thoracoscopy is similar to open thoracotomy, but the procedure is far less invasive, usually requiring that the patient remain in the hospital only 1 day.

Cytopathology of malignant mesothelioma: a study of its patterns and histological bases

We have reviewed the effusion cytology of 51 cases of histologically proven malignant mesothelioma of the pleura (49 cases) and the peritoneum (2 cases). The patient group included 45 males and 6 females, aged 45-83 yr. A cytological diagnosis of malignancy had been rendered on 43 cases, and in 30 of them it was consistent with, or at least suggestive of, a mesothelioma. Diagnostic clues, especially evident in epithelial and biphasic tumors were hypercellularity and/or morular aggregates of malignant cells showing scalloped borders and nuclei with dense chromatin and evident nucleoli. Cytomegaly with multinucleation was also frequently observed. Reactive mesothelial cells were often present along with other non specific features such as red blood cells, fibrin, necrotic debris. In 13 cases, a diagnosis of malignancy was entertained but mesothelioma, although considered, was not reported out because of scantiness of material. In four cases, adenocarcinoma was erroneously diagnosed for the presence of deceptive cell vacuoles. In eight cases, no diagnostic cells were recovered in repeated effusions. The first diagnosis was a cytologic one in 37 patients, Tissue study was performed on autopsy (35 patients) and surgical material. The latter was the only source of histology in six cases. Immunocytochemical investigation was negative for carcinoembryonic antigen in all but one tested cases (1/21) and positive for human milk fat globulin in about one-half of the epithelial and biphasic tumors. In 18 of 21 cases, positivity for combined high- and low-molecular-weight keratins was detected.(ABSTRACT TRUNCATED AT 250 WORDS)

p53 immunostaining in the distinction between benign and malignant mesothelial proliferations using formalin-fixed paraffin sections

The distinction between reactive mesothelium and mesothelioma in pleural biopsy specimens is notoriously difficult, and conventional immunohistochemical markers have provided no relief. The object of this study was to examine the frequency of immunohistochemically detectable p53 overexpression in routinely processed, paraffin-embedded tissue from pleural mesotheliomas and from pleura showing reactive mesothelial hyperplasia, using a polyclonal antibody to formalin-resistant p53 epitopes, and to consider the diagnostic utility of this antibody in the distinction between mesothelioma and reactive mesothelium in pleural biopsy specimens. Immunostaining was enhanced by pepsin predigestion prior to the application of the primary antibody. Positivity occurred in 10/16 epithelial mesotheliomas, 9/19 biphasic mesotheliomas, 2/12 sarcomatous mesotheliomas but in none of 20 reactive pleura. Immunostaining was particularly intense in some of the biopsy specimens, which may be due to the rapidity with which these small pieces of tissue were fixed. In conclusion, this study suggests that p53 immunostaining can help to distinguish epithelial or biphasic mesothelioma from reactive mesothelial hyperplasia in formalin-fixed, paraffin-embedded pleural biopsy specimens.

Epithelial differentiation in gliomas, meningiomas and choroid plexus papillomas

The immunohistological findings using antibodies to different intermediate filaments (glial fibrillary acidic protein, vimentin and two types of cytokeratin) and epithelial membrane antigen are described in 89 gliomas, 19 meningiomas and 8 choroid plexus papillomas (CPPs) from adult patients. All the patients had total or subtotal surgical excision of their tumours with clinical follow up for between 3 and 7 years. The immunohistological results were correlated with the histological features and patient survival. Tumours other than low grade astrocytomas, oligodendrogliomas and anaplastic ependymomas expressed one or more epithelial markers. This immunohistological evidence of epithelial differentiation in the absence of histological epithelial features in gliomas confirms that the two are not necessarily correlated. It is concluded that the expression of epithelial markers in some intradural tumours may reflect aberrant differentiation related to the degree of anaplasia in poorly differentiated astrocytomas and glioblastomas. All the patients with anaplastic epithelial marker-positive gliomas died within 1 year, whereas only 68% of patients with marker-negative tumours died within the follow-up period. In ependymomas and meningiomas, the expression of epithelial markers may reflect their histogenesis, while in malignant CPPs such expression could denote either their aberrant differentiation or histogenetic derivation.

The role of closed pleural needle biopsy in the diagnosis of malignant mesothelioma of the pleura

Malignant mesothelioma of the pleura is a disease that requires a biopsy procedure for a definitive diagnosis. In the past, closed pleural needle biopsy (CPNB) has given poor yields due to the small amount of tissue obtained, and the patient has subsequently been subjected to a diagnostic thoracotomy. In recent years, the availability of more accurate histopathologic tests have enabled the pathologist to make a diagnosis more easily on samples obtained at CPNB. In this retrospective study of 20 consecutive cases of malignant mesothelioma of the pleura diagnosed between 1980 and 1990, we found that a blind CPNB was diagnostic in five of seven procedures and CT-guided CPNB was diagnostic in five of six procedures. An open pleural biopsy (OPB) was diagnostic in ten of ten procedures performed. There were no complications associated with any of the CPNB procedures. We conclude that CPNB is a safe and effective manner of diagnosing malignant mesothelioma of the pleura, and should be attempted prior to OPB.