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

Cytopathology of malignant mesothelioma: a stepwise logistic regression analysis

Twenty-four cytologic features, previously reported to be useful in the distinction of malignant mesothelioma, adenocarcinoma, and benign mesothelial proliferation in serous effusions were assessed. Forty-four cases of malignant mesotheliomas, 46 cases of metastatic adenocarcinomas, and 30 cases of benign mesothelial proliferations were examined for these parameters. When these cytologic features were subjected to a stepwise logistic regression analysis, five features were selected to distinguish malignant mesothelioma from adenocarcinoma. These were true papillary aggregates, multinucleation with atypia, cell-to-cell apposition, acinus-like structures, and balloon-like vacuolation, the latter two features being characteristic of adenocarcinoma. The four variables selected to distinguish malignant mesothelioma from benign mesothelial proliferations were nuclear pleomorphism, macronucleoli, cell-in-cell engulfment, and monolayer cell groups, the latter being a feature of benign proliferations. Using these selected variables, the logistic model correctly predicted 95.4% of cases of malignant mesothelioma versus 100% of adenocarcinoma and 100% of malignant mesotheliomas versus 90% of benign mesothelial proliferations. The results of regression analysis suggest that many of the previously described cytologic features are not important diagnostic discriminators.

Scanning electron microscopy of body fluids

Scanning Electron Microscopic (SEM) examination of body fluid specimens submitted for cytopathological diagnosis is technically easy and can be accomplished within hours. Specimens refrigerated for as long as 72 hr show no significant structural alterations that would interfere with recognition of diagnostically significant cells. SEM is particularly well suited for these specimens because the cells are free floating, and even cells in clusters have "natural" surfaces. Clinical uses of SEM on body fluids include the identification of ambiguous cells, distinction of reactive (benign) mesothelial cells from metastatic adenocarcinoma, and distinction of lymphoid cells from small cell carcinoma of the lung. In addition, SEM of these fluids assists cytologists to better understand the cellular features and associations seen in the light microscope. Ultrastructural analysis can be an important component of the Quality Assurance Plan for those cytodiagnostic laboratories that have access to an electron microscopy facility.

Morphometric analysis of nucleolar organizer regions in benign and malignant peritoneal effusions using backscattered electron microscopy

Nucleolar organizer regions are loops of DNA associated with silver-stainable proteins (AgNORs). In general, malignant cells have more and larger AgNORs than benign cells. An inconsistent argyrophilic method and difficulties in objectively evaluating AgNORs account for some of the reluctance to utilize AgNOR staining as a diagnostic tool to differentiate benign and malignant lesions. Sections from paraffin-embedded cell blocks of 10 cases of benign and malignant peritoneal effusions were stained with a modified AgNOR method. Backscattered electron imaging in the scanning electron microscope, together with image analysis, was used to evaluate more objectively a number of AgNOR parameters and to determine which measurement was the most reliable discriminant of the two types of fluids. One hundred nuclei per case were identified and imaged. In contrast to benign nuclei, AgNORs in malignant nuclei were more numerous (P less than 0.0001) and larger (P less than 0.0001). A cut-off mean AgNOR area of 1.1 microns 2 (P less than 0.0001) correctly categorized all malignant (greater than 1.1 microns 2) and benign (less than or equal to 1.1 micron 2) cases. This system's objectivity and specificity could be used to enhance the cytological interpretation of effusions, where the separation of reactive mesothelial cells and malignant cells is extremely difficult.

Absence of evidence for a significant background incidence of diffuse malignant mesothelioma apart from asbestos exposure

The incidence of diffuse malignant mesothelioma is rising. Physicians can diagnose a disease only when they know that it exists, so one explanation for the rise in incidence is more widespread appreciation of the clinical and pathological features of the disease. Modern pathology has ascribed specific requirements for the diagnosis of diffuse malignant mesothelioma. A priori one cannot assume that these requirements have increased the likelihood of the diagnosis because the requirements also can serve to exclude the diagnosis depending on the findings. Most cases of diffuse malignant mesothelioma are suspected by macroscopic and routine microscopic techniques that have been available since the last part of the nineteenth century. Although single reported instances of some pulmonary diseases have survived from the nineteenth century, pathologists did not identify enough cases to convincingly establish the existence of diffuse malignant mesothelioma of the pleura as an entity until the 1930s or 1940s. One must conclude that the background level of diffuse malignant mesothelioma in Europe and in the United States prior to 1930 was extremely low. No case was detected at the Massachusetts General Hospital until 1946.

Immunocytochemistry of malignant mesothelioma: OV632 as a marker of malignant mesothelioma

In pleural or ascitic effusions the cytomorphological distinction of adenocarcinoma cells, reactive mesothelial cells, and malignant mesothelioma cells often causes a diagnostic dilemma. The value of immunocytochemistry was investigated on cytological smears of 24 well-established cases of malignant mesothelioma, a selected series of 31 metastatic adenocarcinomas, and 20 smears of patients without known malignancy. In these smears we scored the immunoreactivity with a panel of four monoclonal antibodies. In addition to antibodies for epithelial membrane antigen (EMA) and carcinoembryonic antigen (CEA), the monoclonal antibody MOC31 and the ovarian carcinoma specific antibody OV632 were incorporated in the panel. With none of these four antibodies was immunostaining of reactive mesothelial cells found. CEA- and MOC31-positive tumour cells were frequent in metastatic adenocarcinomas, but occurred rarely in malignant mesotheliomas. EMA-positive tumour cells were found in all metastatic adenocarcinomas (100 per cent) and in most malignant mesotheliomas (83 per cent). In addition to the expected reactivity of OV632 with ovarian carcinomas, 22 of 24 malignant mesotheliomas contained immunopositive tumour cells, while only a small proportion of non-ovarian adenocarcinomas reacted with this antibody. This selective staining of malignant mesothelioma cells, but not reactive mesothelial cells, with OV632 now permits the positive identification of malignant mesothelioma cells in male patients.

Establishment and characterization of five human malignant mesothelioma cell lines derived from pleural effusions

Malignant mesothelioma (MM) is an aggressive tumour of the serosal cavities which is associated with exposure to asbestos. Studies of this tumour have been limited by a paucity of well-characterized human MM cell lines. In this study, 5 human MM cell lines were established from pleural effusions of patients with this malignancy. All 5 patients were males with known crocidolite asbestos exposure, who had received no treatment for their disease and in whom the diagnosis was confirmed by cytology, histology and electron microscopy (EM). These lines have been in culture from 11 to 25 months, and all of them for more than 18 passages. The appearance of the cells in culture was extremely varied; in 3 of the lines they were spindle-shaped with few vacuoles (JU77, LO68 and ONE58); in 1 line they had a thick, stellate shape with vacuoles (NO36) and in 1 they were very pleomorphic in both shape and size with irregular membranes and numerous vacuoles [DeH128 (M)]. Upon reaching confluence, cells in 3 of the 5 lines assumed the cobblestone-like pattern characteristic of epithelial-type cells, whereas in the other 2 (LO68 and ONE58) they remained spindle-shaped. All 5 lines demonstrated a loss of contact inhibition (i.e., piling) at confluence. Minimum doubling times varied significantly from 18 hr (JU77) to more than 30 hr [DeH128 (M)]. Cytological examination showed characteristic mesothelial/mesothelioma morphology, and epithelial membrane antigen (EMA) and cytokeratin were demonstrated in cells from all 5 lines. These cells lacked CEA and epithelial mucin. The presence of cell junctions, glycogen and numerous long, thin, branching microvilli was readily demonstrable by EM. All lines had abnormal karyotypes, with the modal chromosome number varying from 40 to 80. Variable chromosome numbers, numerous structural rearrangements and unrecognizable marker chromosomes were readily observed; however, the only consistent change seen was del 6q21 in 4 of the 5 lines. The establishment of these 5 cultured human MM cell lines now provides an opportunity for comparative study of several aspects of the biology of MM in vitro as well as screening new treatment modalities.

Distinguishing malignant mesothelioma from pulmonary adenocarcinoma: an immuno-histochemical approach using a panel of monoclonal antibodies

A panel of six monoclonal antibodies (MAbs) was employed to evaluate antigen expression in pulmonary adenocarcinomas and mesotheliomas. Monoclonal anti-human milk fat globulin (HMFG-2), anti-carcinoembryonic antigen (NP-2), anti-epithelial membrane antigen (EMA), anti-cytokeratin (PKK-1), anti-tumor-associated antigen 72 (B72.3), and anti-human myelomonocytic antigen (Leu M-1) antibodies were used to localize their respective antigens in formalin-fixed, paraffin-embedded tumors by using the avidin-biotin-complex immunoperoxidase technique. In all, 28 mesotheliomas obtained from Ohio State University Anatomic Pathology files and from a Southwest Oncology Group (SWOG) protocol were compared to 22 pulmonary adenocarcinomas by using this MAb panel. None of the mesotheliomas demonstrated positive staining with MAbs NP-2 (anti-CEA) or Leu M-1. However, 95% (21/22) of adenocarcinomas stained with one of these two antibodies. Although neither of these two MAbs stained all adenocarcinomas, each antibody demonstrated positive immunostaining in more than 90% of the adenocarcinomas studied. Therefore, MABs NP-2 and Leu M-1 are, individually, quite useful for distinguishing mesothelioma from adenocarcinoma. However, in our study, no single MAb could be used to distinguish these two tumor types in every case. MAb B72.3 stained 91% (20/21) adenocarcinomas but also stained 7% (2/28) of mesotheliomas. MAb HMFG-2 reacted positively with 95% of adenocarcinomas, but also stained 39% of the mesotheliomas, usually in a membranous pattern. MAbs EMA and PKK-1 were not found useful in distinguishing mesothelioma from adenocarcinoma. We conclude that MAbs Leu M-1 and NP-2 were both useful in distinguishing mesothelioma from pulmonary adenocarcinoma in that positive staining was demonstrated in adenocarcinomas and not mesotheliomas.

A morphometrically-based classification rule for the diagnosis of primary mesothelial lesions

A computer-aided morphometrical study was performed on histological specimens of reactive hyperplastic (n = 10) and malignant (n = 17) mesothelium. For each cell, seven nuclear features were measured and 13 parameters computed. Using stepwise variable selection, discriminant analysis chose the nuclear contour index, the standard deviation of the nuclear area, and the mean of the nuclear perimeter as discriminating features between hyperplastic and malignant mesothelium. The coefficients of these variables were included in a discriminant function which gave perfect discrimination between the two groups of lesions. When the function was assessed on a test set of hyperplastic (n = 10) and malignant (n = 17) mesothelial lesions treated as 'unknown', complete separation between these two diagnostic categories was achieved. This classification rule may help to increase the level of confidence with which a histological diagnosis of mesothelioma can be established.

Cytogenetic analysis of malignant mesothelioma

Cytogenetic analyses of 40 confirmed malignant mesotheliomas (MMs) are reported. Pleural effusion cells were studied in 90% of the cases by direct method or after culture or both. Biopsy and ascites fluid were also analyzed in some patients. A normal karyotype was found in nine cases, and complex karyotypic abnormalities were observed in 30 cases. In one case, analyzable metaphases were not obtained. The chromosomal changes were all complex and heterogeneous; no consistent presumably specific abnormality was detected. Nevertheless, two main patterns of nonrandom abnormalities were observed: 1) loss of chromosomes 4 and 22, 9p, and 3p in the most of the abnormal cases and corresponding to a hypodiploid and/or hypotetraploid modal chromosome number; and 2) gain of chromosomes 7, 5, and 20 with deletion or rearrangement of 3p as well in the hyperdiploid cases, which were a minority in our series. These findings are discussed in view of other reported cytogenetic studies of MM, asbestos exposure, and possible mechanisms of malignant transformation.

Cytopathology of malignant mesothelioma. Reappraisal of the diagnostic value of collagen cores

The identification of malignant mesothelial cells in cytological smears prepared from serous effusions is still hampered by the lack of features specific for mesothelial differentiation. We examined the diagnostic value of collagen cores within clusters of tumour cells in cytological smears prepared from effusions from 43 patients with malignant mesothelioma and of 62 cases of metastatic adenocarcinoma. In Giemsa-stained smears collagen cores were detected in 51% of the cases of malignant mesothelioma and in none of the smears with metastatic adenocarcinoma. Using the Azan stain, collagen cores were detected in 64% of the malignant mesotheliomas and 4% of the adenocarcinomas. Immunoelectron microscopy demonstrated that the collagen cores are largely composed of collagen type III fibrils and some elastin embedded in a homogenous extracellular matrix. It can be concluded that the presence of collagen cores within clusters of tumour cells is highly suggestive of mesothelial differentiation and a common finding in malignant mesothelioma.

"Thick" cell membranes revealed by immunocytochemical staining: a clue to the diagnosis of mesothelioma

The distinction of malignant mesothelioma from metastatic adenocarcinoma in pleural effusions and biopsies is frequently a diagnostic problem. Immunocytochemical staining of 13 malignant mesotheliomas, eight primary adenocarcinomas of the lung, five metastatic adenocarcinomas of the lung, and 20 primary adenocarcinomas in extrapulmonary sites with a monoclonal antibody to epithelial membrane antigen (EMA) revealed "thick" cell membranes in all cases of mesothelioma. This distinctive pattern of staining was seen in the periphery of cell clusters and circumferentially around individual cells in cytologic preparations, cell blocks, and tissue sections. Intracellular and intercellular acini were also outlined by anti-EMA, and long intraluminal microvillous projections were demonstrated. Weak cytoplasmic staining was only rarely seen in mesothelioma cells. This membranous staining pattern was not observed in adenocarcinomas, which displayed strong and diffuse cytoplasmic staining. The immunocytochemical demonstration of thick and spiky membranes circumferentially disposed around individual cells corresponds to aberrant microvilli, a diagnostic clue in the recognition of malignant mesothelioma.

Evaluation of impact of immunocytochemical techniques in cytological diagnosis of neoplastic effusions

A prospective study (1984-87) on the immunocytochemical identification of cancer cells in effusions using HMFG2 monoclonal antibody, and in addition, monoclonal anti-CEA and B72.3 antibodies in cases of suspected mesothelioma, was undertaken. On the basis of cytology alone, of a total of 2362 pleural, peritoneal, and pericardial effusions, 525 cases were diagnosed as positive and 1485 as negative for neoplastic cells, while in 352 (15%) specimens from 307 patients the diagnosis was doubtful. Sections of the embedded sediment of doubtful cases were tested with HMFG2 antibody and proved positive in 215 cases, negative in 108, and inconclusive in 29. The results were checked by following the clinical outcome of the cases. The method was specific in identifying cancer cells in cases at best diagnosed as suspicious on the basis of cytology alone; this represents a clear diagnostic gain. Sensitivity of the test, however, was relatively low (41%). Combined cytological and immunocytochemical characteristics (CEA negative and only some of the neoplastic cells positive with HMFG2 and B72.3 monoclonal antibodies) permitted diagnosis on the effusions of most cases of mesothelioma. The impact of the diagnosis on the progress of the disease was not appreciable as no difference in outcome was noted, irrespective of whether cancer cells had been recognised. The occurrence of an effusion remains an ominous sign in most patients treated for cancer.

Characterization of three human malignant mesothelioma cell lines

Three human malignant mesothelioma cell lines, designated Mero-14, Mero-25, and Mero-41, have been isolated from effusions and from autopsy material of confirmed cases of malignant mesothelioma. Light and electron microscopy, cytogenetics, growth requirements, and intermediate filament expression of these cell lines were studied and, where possible, compared with the original tumor material of the patient. Cytologic and ultrastructural morphology was consistent with the mesothelial nature of the cells. All cell lines displayed a hyperdiploid karyotype similar to that of the tumor cells obtained directly from the patient. All three malignant mesothelioma cell lines had marker chromosomes 1, 3, 9, and 22, as well as other markers that were occasionally present in these cell lines and in other malignant mesotheliomas studied. Growth kinetic studies in medium supplemented with epidermal growth factor (EGF) showed increased proliferation and a decreased proliferation in medium supplemented with hydrocortisone (HC) or EGF plus HC. The three malignant mesothelioma cell lines were positive for the cytokeratins 7, 8, 18, and 19 based on immunofluorescence and immunoblotting tests with chain-specific monoclonal antibodies. The characteristics of these cell lines support the assumption that Mero-14, Mero-25 and Mero-41 are derived from malignant mesotheliomas and have retained their original character.

Establishment of human malignant mesothelioma cell lines

Seventeen human malignant mesothelioma cell lines were isolated from 61 samples (46 effusions, 9 biopsies and 6 tumors obtained at autopsy) collected from patients with a confirmed malignant mesothelioma. The method used is given in detail. Cytogenetic analysis of growing cultures is the best indicator to determine whether the observed proliferation concerns malignant or normal mesothelial cells. The addition of epidermal growth factor (EGF) and hydrocortisone (HC), or EGF alone, to the culture medium increases the chances of successful isolation of a malignant mesothelioma cell line.

Nine-year survival in a case of untreated peritoneal mesothelioma

A patient with malignant mesothelioma of the peritoneum, which has been untreated except for regular paracentesis for effusions, has remained alive and generally-well for nine years. The poor prognosis that usually is ascribed to this disease may not be applicable universally.

Concentration of hyaluronic acid in pleural fluid as a diagnostic aid for malignant mesothelioma

Hyaluronic acid (HA) was determined with a radiometric assay in the serum and pleural fluid of 85 patients with pleural effusions, including 15 with malignant mesothelioma, 32 with other cancer, 31 with nonmalignant inflammatory diseases, and seven with congestive heart failure. With a cutoff level at 100 mg/L, the pleural fluid concentration of HA was raised in 73 percent of patients (11 of 15) with malignant mesothelioma and in 23 percent with nonmalignant inflammatory diseases, but in none with other cancer and in none with congestive heart failure. The median concentration of pleural fluid HA was significantly higher in patients with mesothelioma than in those with other cancer (p less than 0.005). Determination of carcinoembryonic antigen (CEA) in pleural fluid further helped to differentiate between mesothelioma and other types of cancer; concentrations of CEA above 10 micrograms/L were found in four of 15 (27 percent) patients with mesothelioma, but in 38 percent of the patients with other cancer. We concluded that in the differential diagnosis of pleural effusions associated with malignant tumors a high concentration of HA in pleural fluid combined with a low concentration of CEA suggests malignant mesothelioma as opposed to other types of cancer.

Induction of lung tumors and peritoneal mesotheliomas in F344 rats given intragastric N-propyl-N-nitrosourea and histochemical, immunohistochemical, and ultrastructural characteristics of induced mesotheliomas

N-Propyl-N-nitrosourea is a strong leukemogen that induces myelogenic leukemia in Donryu rats and thymic lymphoma in F344 rats when administered in drinking water. In the present study, a single or multiple doses of PNU (total 500 mg/kg body weight) was given to young male and female F344 rats via a stomach tube. The results demonstrated that the percentage of tumor-bearing rats was 100% in all PNU-treated male groups, while that of the control group was 46%. Predominant tumors induced by PNU in male rats were lung adenoma/adenocarcinoma followed by peritoneal mesothelioma, and forestomach papilloma. In females, the tumor incidence of PNU-treated groups varied between 58% and 92% while that of the control group was 42%. Although pituitary tumor was the most frequent tumor in PNU-treated female rats, it was thought to be spontaneous since its incidence in each experimental group was not statistically different from that of the control group. Lung tumors and forestomach papillomas were also induced by PNU in female rats. No thymic lymphoma, however, was found in any of the PNU-treated groups of either sex. Lung tumors developed in almost all PNU-treated male rats and in about one-third of PNU-treated female rats. Mesothelioma was induced only in male rats, and its incidence depended on the treatment schedule. Induced mesotheliomas were extensively examined histologically, histochemically, immunohistochemically, and electron microscopically.

Thoracoscopy: assessment of a physician service and comparison of a flexible bronchoscope used as a thoracoscope with a rigid thoracoscope

The practicality of physicians performing thoracoscopy for diagnostic purposes was assessed in 30 patients with pleural effusions of unknown cause. A rigid thoracoscope was compared with a fibreoptic bronchoscope used as a flexible thoracoscope and the diagnostic adequacy of biopsy specimens obtained with the two instruments assessed. The two instruments were inserted by a physician in the bronchoscopy suite using local anaesthesia. The procedure proved safe, acceptable, and diagnostically effective. The rigid thoracoscope proved a more satisfactory instrument but the fibreoptic bronchoscope, with minor adaptations, may be used for thoracoscopy.

Diagnostic histochemical and immunohistochemical studies in malignant mesothelioma

This study was undertaken to evaluate the relative utility of histochemical and immunohistochemical stains in diagnosing malignant mesothelioma of the thorax. We performed a battery of histochemical stains, including periodic acid Schiff (PAS) with and without diastase, mucicarmine, colloidal iron (Coll Fe) with and without hyaluronidase, and immunohistochemical stains for keratin and carcinoembryonic antigen (CEA) on 12 pleural mesothelioma specimens obtained from 11 patients, five primary pulmonary adenocarcinomas, and one metastatic adenocarcinoma each to pleura and pericardium. All diagnoses were established by autopsy or thorough clinical and surgical evaluation. The diagnosis of mesothelioma was established following rigid anatomic criteria. All tissue was formalin fixed and paraffin embedded. Commercially available reagents and antisera were used in all cases. Results showed a high rate of positivity for keratin and hyaluronidase-sensitive Coll Fe in the mesotheliomas while adenocarcinomas were uniformly positive for CEA and keratin and generally positive for PAS-D (diastase) and mucicarmine. Mesotheliomas were negative for CEA, mucin, and PAS-D. Positive keratin staining was also seen in the spindle cell components of mesotheliomas. Immunohistochemical stains often added significantly to our ability to establish the diagnosis of mesothelioma with confidence, since they were more frequently and more clearly positive than histochemical stains.

Spontaneous mesotheliomas in Fischer rats--a histological and electron microscopic study

Seventeen mesotheliomas from 395 untreated male Fischer 344/DuCrj rats were studied by light and electron microscopy to define the morphological characteristics of the tumors. In 16 out of 17 rats, mesotheliomas were observed in the abdominal and/or scrotal sac, and the other one was localized on the pleura. Grossly, tumors were yellow-brown with various-sized multiple modules growing irregularly over the surface of the serosa. Microscopically, they varied from complex papillary to sessile nodular growths. Tumor cells were cuboidal to polygonal with round to oval nuclei, and were sometimes arranged in tubule-like structures. Occasionally, the cells contained Mowry's colloidal iron positive materials, which were negative following prior incubation with hyaluronidase. Furthermore, intracellular keratins were detected using the peroxidase-antiperoxidase method. Ultrastructural features of tumor cells included numerous microvilli, a basement membrane, junctional complexes, abundant cytofilaments, dilated rough surfaced endoplasmic reticulum cisternae, and a well-developed Golgi apparatus. The morphological characteristics of these tumors in Fischer 344 rats were consistent with those in humans and with experimentally induced counterparts in rats. The histogenesis of these tumors and the variability in their incidence following oral administration of chemical carcinogens is discussed.

Simultaneous immunoenzyme staining of vimentin and cytokeratins with monoclonal antibodies as an aid in the differential diagnosis of malignant mesothelioma from pulmonary adenocarcinoma

The occurrence and coexpression of the cytoskeletal proteins vimentin and cytokeratins were studied in malignant mesotheliomas and pulmonary carcinomas. For this purpose a double immunoenzyme staining with monoclonal antibodies was developed which made it possible to visualize vimentin and cytokeratins simultaneously within the same cell. A clear distinction between stromal cells (vimentin only) and tumour cells was also obtained. A total of 12 mesotheliomas (six mixed type and six epithelioid type) and 13 carcinomas (eight adenocarcinomas and five large cell undifferentiated carcinomas) were studied. The results revealed a clear difference between mesotheliomas and adenocarcinomas: 11 of 12 mesotheliomas showed coexpression of vimentin and cytokeratins in at least 50% of the tumour cells, while in seven of the eight adenocarcinomas none or only a few cells could be seen with this coexpression. In the undifferentiated large cell carcinomas three of five expressed both components, but in less than 25% of the cells. It is concluded that a reliable double immunoenzyme staining of vimentin and cytokeratins can be used as an additional means to distinguish malignant mesothelioma from pulmonary adenocarcinoma.

Diffuse malignant mesothelioma of pleura. Diagnosis and survival in 92 cases

Clinical, radiographic, surgical, and pathologic findings and survival in 92 patients with diffuse malignant mesothelioma (DMM) of the pleura who were examined at the Mayo Clinic between 1950 and 1980, were studied retrospectively. With the use of defined criteria and ordinary tissue stains, the 92 cases were classified into the following histologic subtypes: purely epithelial, 42 cases; mixed, 29 cases; and sarcomatous, 21 cases. Eight of the sarcomatous cases were desmoplastic. Median survivals were 12, 5, and 3 months for the patients in the epithelial, mixed, and sarcomatous groups, respectively. Survival was significantly longer for patients with epithelial DMM. Women survived longer than men but more often had epithelial DMM. Early disease manifested as multiple discrete pleural nodules, predominantly on the parietal pleura. However, nine patients had a dominant mass. Radiographic signs especially suggestive of DMM were nodular pleural thickening, irregular thickening of interlobar fissures, a dominant mass, or decreased volume of the affected hemithorax.

New marker for mesothelioma: an immunoperoxidase study

An antibody was raised against a protein isolated from the cytoplasm of mesothelioma cells. It was subsequently used in an immunoperoxidase procedure on formalin fixed, paraffin embedded tissue sections. A representative sample of benign and malignant tumours from all the systems of the human body was examined. All the tumours derived from coelomic surfaces (mesotheliomas of pleura, peritoneum, and ovary, and adenomatoid tumour of epididymis) reacted with the antibody. No other tumour tested in this study expressed the protein. These findings indicate that the antibody may be useful in the identification of mesothelioma cells in both histological and cytological diagnostic routine practice when morphological interpretation is in doubt.

Pleural fluid CEA levels in the diagnosis of malignant mesothelioma

A study was undertaken to investigate whether the levels of carcino-embryonic antigen (CEA) in serous effusions helped distinguish between primary mesothelioma and metastatic adenocarcinoma in a body cavity. The investigation was designed to assess the role of the assay only when cytological analysis of the fluid had already shown the presence of malignant cells. No case of mesothelioma studied had levels of CEA above 2.9 ng/ml, whereas 67% of the adenocarcinomas tested were above 15 ng/ml. The test is helpful, therefore, in differentiating between these two types of malignant effusions.

Epithelial membrane antigen and cytokeratin expression by meningiomas: an immunohistological study

Thirteen meningiomas of varying light microscopic features were studied immunohistologically using a panel of monoclonal antibodies directed against epithelial, mesenchymal, and neural components. All 13 meningiomas showed expression of epithelial membrane antigen, vimentin, and S100 protein, as did normal meninges. Five of the 13 meningiomas also showed focal expression of cytokeratins, with double labelling showing expression of cytokeratins and vimentin by different cells. The cytokeratin expression was especially noticeable in cells surrounding the hyaline bodies of meningiomas. These results provide further evidence that meningiomas have features of both mesenchymal and epithelial tissues.

Malignant mesothelioma cells in sputum

In five patients with malignant mesothelioma of pleura, malignant cells, presumably derived from intrapulmonary deposits, were found in sputum specimens. The cells presented mainly as papillary aggregates of epithelial-like cells, in most cases without specific identifiable mesothelial cell features. In one patient, the specimen was received early in the diagnostic work-up and led to a strong consideration of the diagnosis of adenocarcinoma. In the remainder, the finding was incidental, occurring after the diagnosis of mesothelioma had been established. The cases are reported to draw attention to this phenomenon, previously unreported in the cytologic literature, and to emphasize that the finding of malignant cells in sputum does not preclude the diagnosis of malignant mesothelioma.

The role of concurrent determinations of pleural fluid and tissue carcinoembryonic antigen in the distinction of malignant mesothelioma from metastatic pleural malignancies

A combined determination of pleural fluid and tissue carcinoembryonic antigen (PF-CEA and T-CEA) by radioimmunoassay and immunoperoxidase staining technique respectively was performed in patients with malignant mesotheliomas (12), metastatic pleural carcinomas (17) and benign pleural diseases (seven). All PF-CEA-positive (greater than 39 ng/ml) cases were T-CEA-positive metastatic carcinomas. In contrast, 4/30 PF-CEA-negative (less than 39 ng/ml) cases were T-CEA-positive metastatic carcinomas (three cases) and idiopathic pleuritis (one case). These results suggest that CEA, though present in the tumour, is not always released in measurable amounts in effusions. Hence T-CEA content should be determined in the PF-CEA-negative cases when an early and definite diagnosis of tumour type is required to enable correct management of these patients. These ancillary tests aim at enhancing the level of confidence of the routine morphological diagnosis of serous surface malignancies in living patients using minimal intervention instead of resorting to open chest surgery.

S-100 protein in malignant mesotheliomas

Recently, the presence of S-100 protein has been described in a few tissues that are not of neuro-ectodermal origin. Here we report the presence of S-100 protein in epithelial and biphasic malignant mesotheliomas and one of seven reactively proliferating mesothelial lesions. Sarcomatous malignant mesotheliomas, six of seven reactive mesothelial lesions and normal mesothelium were without S-100 protein. The presence of S-100 protein in mesothelial cells may indicate intense proliferation.

Comparison of tumour markers in malignant mesothelioma and pulmonary adenocarcinoma

Immunohistological methods were used to investigate the presence of carcinoembryonic antigen, beta 1 pregnancy specific glycoprotein, beta subunit of human chorionic gonadotrophin, human placental lactogen, calcitonin, and keratin in formalin fixed tissue from 29 malignant mesotheliomas and 27 pulmonary adenocarcinomas. Malignant mesotheliomas were negative for tumour markers except for the beta subunit of human chorionic gonadotrophin and keratin, one and 13 cases respectively being positive for these. Pulmonary adenocarcinomas, however, were frequently positive for tumour markers--namely, carcinoembryonic antigen, beta 1 pregnancy specific glycoprotein, beta subunit of human chorionic gonadotrophin, human placental lactogen, calcitonin, and keratin. The presence of carcinoembryonic antigen and beta 1 pregnancy specific glycoprotein within an intrathoracic tumour is strong evidence against its being of mesothelial origin.

The use of vimentin antibodies in the diagnosis of malignant mesothelioma

An immunohistochemical investigation of vimentin, an intermediate filament, was carried out on formalin fixed paraffin embedded sections of 44 malignant mesotheliomas of the pleura and 24 pulmonary adenocarcinomas, in order to assess its value in differential diagnosis. Seventy-five percent of the malignant mesotheliomas showed positive staining for vimentin. An unexpected finding was the presence of vimentin in 46% of the pulmonary adenocarcinomas. In either case there was no correlation between the presence of vimentin and the histological types or grades of differentiation. The overall level of vimentin staining was significantly greater in the malignant mesotheliomas than in the pulmonary adenocarcinomas but no single antibody dilution was found to provide clear cut separation of the two groups. Vimentin does not appear to be a simple discriminatory marker of malignant mesothelioma.