The value of 'mesothelium-associated' antibodies in distinguishing between metastatic renal cell carcinomas and mesotheliomas

AIMS: Despite increasing usage of mesothelium-associated antibodies in diagnosis, a meta-analysis of studies analysing these antibodies in relation to distinguishing mesothelioma from renal cell carcinoma shows a paucity of published data. Given the clinical importance of elucidating this differential diagnosis, we compared the phenotypes of these two tumours using a panel of antibodies comprising recently described 'mesothelium-associated' antibodies and the more established 'epithelium-associated' antibodies. METHODS AND RESULTS: We applied an antibody panel comprising calretinin, cytokeratin (CK)5/6, thrombomodulin, carcinoembryonic antigen (CEA), BerEP4 and BCA225 to 37 cases of pleural mesotheliomas and 40 cases of renal cell carcinoma (27 primary tumours and 13 metastatic to the pleura). All mesotheliomas were either purely epithelioid or of mixed type. Cases of renal cell carcinoma were graded and classified as to cell type and architecture. For mesotheliomas, 0% stained for CEA, 16% for BerEP4, 83% for BCA225, 78% for CK5/6, 86% for thrombomodulin and 97% showed nuclear staining for calretinin. For renal cell carcinomas, 0% stained for CEA, 50% for BerEP4, 88% for BCA225, 5% for CK5/6, 32% for thrombomodulin and 10% showed nuclear staining for calretinin. CONCLUSION: Calretinin, CK5/6 and BerEP4 appear the most useful antibodies in helping to distinguish between renal cell carcinomas and mesotheliomas, although BerEP4 was not particularly sensitive for renal cell carcinomas. Thrombomodulin was not as specific as the other 'mesothelium-associated' antibodies in this study, reflecting how staining for mesothelium-associated antibodies varies in carcinomas from different primary sites, and such variations should be taken into account when assessing the differential diagnosis of mesothelioma. In cases where doubt remains over distinguishing metastatic renal cell carcinoma from mesothelioma, data from such a panel should be viewed with caution and assessed in association with clinical, imaging and morphological features.     

Ber EP4 and epithelial membrane antigen aid distinction of basal cell, squamous cell and basosquamous carcinomas of the skin

AIMS: Seventy-five skin tumours were studied to investigate the value of immunohistochemistry in differentiating basal cell, squamous cell and basosquamous carcinomas of the skin. METHODS AND RESULTS: Archived paraffin-embedded tissue samples of basal cell carcinomas (n = 39), squamous cell carcinomas (n = 23) and basosquamous carcinomas (n = 13) were stained immunohistochemically using a panel of antibodies. All of the basal cell carcinomas stained positively for Ber EP4, in contrast to the group of squamous cell carcinomas, that showed no staining. Basosquamous carcinomas all showed at least some areas of Ber EP4 positivity. None of the basal cell carcinomas, but most of the squamous cell carcinomas (22 of 23) expressed epithelial membrane antigen (EMA). Only one of the basosquamous carcinomas expressed EMA positivity focally. CAM 5.2, carcinoembryonic antigen (CEA) and 34betaE12 antibodies lacked specificity in relation to the different tumour types. CONCLUSION: Distinction of basal and squamous cell carcinomas of the skin can be readily achieved with routine immunohistochemistry using Ber EP4 and EMA. Identification of basosquamous carcinoma is also facilitated with this method.     

Mesothelioma-binding antibodies: thrombomodulin, OV 632 and HBME-1 and their use in the diagnosis of malignant mesothelioma

The aim of this study was to examine the expression of three putative mesothelioma-binding antibodies, thrombomodulin, OV 632 and HBME-1 in 42 malignant mesotheliomas (27 pleural and 15 peritoneal) and 32 pulmonary adenocarcinomas. Evaluation of their use in differentiating between the mesotheliomas and pulmonary adenocarcinomas was assessed. Thrombomodulin was expressed by 22 of 42 (52%) mesotheliomas but was seen in eight of 12 pure epithelial-type mesotheliomas of the pleura and in all four papillary epithelial peritoneal mesotheliomas. For pure epithelial mesotheliomas thrombomodulin was 75% sensitive. Only two of 32 pulmonary adenocarcinomas were immunoreactive yielding a 94% specificity for thrombomodulin. In comparison, OV 632 and HBME-1 showed 67% and 62% antibody sensitivity, respectively, for malignant mesothelioma but this was accompanied by low specificity (OV 632, 37%; HBME-1, 28%). Both OV 632 and HBME-1 are considered unsuitable for use in differentiating between mesotheliomas and pulmonary adenocarcinomas. We advocate the use of thrombomodulin as a mesothelioma-binding antibody in the standard panel of antibodies used in the evaluation of malignant mesothelioma.     

Thrombomodulin expression in malignant pleural mesothelioma and pulmonary adenocarcinoma.

Thrombomodulin (TM) is a glycoprotein of molecular weight 75,000 kd that is normally present in restricted numbers of cells, including endothelial and mesothelial cells. In this study, the authors tested the possibility of using anti-TM to facilitate the diagnosis of mesothelioma. All of the 31 mesotheliomas and the two mesothelioma cell lines (MS-1 and MS-2) tested were stained positively with anti-TM. The specificity of anti-TM staining in mesothelioma cells was further confirmed by in situ hybridization of MS-1 cells with a TM-specific probe. The expression of TM in MS-1 cells was increased markedly when these cells were induced by 12-0-tetradecanyl phorbol 13-acetate (TPA) to differentiate. The expression of TM in mesothelioma cells, however, did not correlate with any particular phase of the cell cycle. In an attempt to differentiate pleural mesothelioma from pulmonary adenocarcinoma, the authors compared the expression of TM, carcinoembryonic antigen (CEA), and Leu M1 in these two types of tumors. Only four of 48 (8%) pulmonary adenocarcinomas were stained positively by antibodies to TM. Therefore, immunohistochemical staining with antibodies to TM yielded 100% sensitivity and 92% specificity for diagnosis of mesothelioma. All of the mesotheliomas stained negatively for CEA and Leu M1, except for one, which showed minimal focal positivity for Leu M1. In contrast, 79% and 60% of adenocarcinomas stained positively for CEA and Leu M1, respectively. These findings suggest that immunocytochemical staining with anti-TM should be added to the battery of tests to increase the diagnostic sensitivity and specificity for differentiating mesothelioma from pulmonary adenocarcinoma.     

HBME-1 and antithrombomodulin in the differential diagnosis of malignant mesothelioma of pleura.

AIMS: To determine the usefulness of antibodies HBME-1 and antithrombomodulin in the differential diagnosis of malignant mesothelioma of the pleura. METHODS: Using microwave antigen retrieval and streptavidin-biotin complex horseradish peroxidase immunohistochemistry the above antibodies were used to stain sections of 57 malignant mesotheliomas, 17 reactive pleural hyperplasias, 23 cases of carcinoma metastatic in pleura, 20 primary ovarian cell carcinomas, and 20 primary renal cell carcinomas. RESULTS: Eighty six per cent of mesotheliomas and 82% of reactive mesothelial hyperplasias stained strongly with HBME-1. However, 48% of carcinomas metastatic to pleura also stained, as did all serous ovarian carcinomas. Seventy two per cent of mesotheliomas and 24% of reactive mesothelial hyperplasias stained strongly with the antithrombomodulin antibody; 86% and 88%, respectively, of these cases showed staining of any type. While 26% of metastatic carcinomas showed some staining with antithrombomodulin, only one third of these (9%) showed strong, yet focal, staining. Of 40 ovarian and renal carcinomas only two (5%) showed any staining with antithrombomodulin. CONCLUSIONS: HBME-1, although a sensitive mesothelial marker, is not sufficiently specific to be useful diagnostically, as almost half of carcinomas metastatic to pleura also stained positive. Antithrombomodulin is also a sensitive mesothelial marker and is sufficiently specific to be a useful discriminator, positively identifying, in appropriate circumstances, the mesothelial nature of a cell population.     

Calretinin, thrombomodulin, CEA, and CD15: a useful combination of immunohistochemical markers for differentiating pleural epithelial mesothelioma from peripheral pulmonary adenocarcinoma

The distinction between pleural epithelial mesothelioma and peripheral lung adenocarcinoma involving the pleura is still an important diagnostic problem for surgical pathologists. The aim of our study was to identify the most specific and sensitive markers for the positive identification of mesothelioma to select a limited, appropriate panel of antibodies to differentiate between mesothelioma and adenocarcinoma. Forty-two cases of epithelial mesotheliomas and 23 cases of pulmonary adenocarcinomas were stained with the following antibodies: anticalretinin, antithrombomodulin, anti-CD44H, and monoclonal antibody HBME-1. We also studied the value of other markers in current use: cytokeratins AE1/AE3 and CAM5.2, epithelial membrane antigen (EMA), carcinoembryonic antigen (CEA), Ber-EP4, B72.3, and CD15. Of the mesotheliomas, 42 stained for calretinin, 39 (92.8%) for thrombomodulin, 42 stained for CD44H, and 41 (97.6%) stained for HBME-1. Among negative markers, 4 (9.5%) mesothelioma cases stained for CEA, 5 (11.9%) stained for Ber-EP4, 6 (14.2%) stained for B72.3, and 2 (4.7%) stained for CD15. Of the lung adenocarcinomas, 2 (8.7%) cases showed reactivity for calretinin, 5 (21.7%) for thrombomodulin, 13 (56.5%) for CD44H, all for HBME-1, 22 (95.6%) for CEA, 22 (95.6%) for Ber-EP4, 8 (34.7%) for B72.3, and all for CD15. In conclusion, calretinin and thrombomodulin were the most specific positive mesothelial markers, whereas CD44H and HBME-1 showed high sensitivity but very low specificity. Among negative markers, we advocate the use of CEA and CD15 which were the most specific in differentiating mesotheliomas from adenocarcinomas.     

Cytological differential diagnosis among adenocarcinoma,epithelial mesothelioma,and reactive mesothelial cells in serous effusions by immunocytochemistry

The objective of the study is to estimate the expression of some antibodies in the metastatic adenocarcinomas, malignant epithelial mesotheliomas, and reactive mesothelial cells in serous effusions and to choose effective panel to the differential diagnosis. Totally 113 effusion cytology samples (80 pleural fluid, 30 ascitic, and 3 pericardial fluid) from 60 cases of metastatic adenocarcinoma (ACA), 18 cases of malignant epithelial mesothelioma (MM), and 35 cases of reactive mesothelium (RM) were included in this study. The cytological diagnoses of these cases were confirmed by histopathology or clinical datas. Smears and cell blocks were prepared for each case. Immunocytochemical study was performed on the cell block sections. The sensitivity of E‐cadherin, CEA, MOC‐31, and Ber‐EP4 for adenocarcinoma was 86.7%, 80%, 70%, and 76.4%, respectively. The specificity was 98.1%, 96.2%, 92.5%, and 86.8%, respectively. The sensitivity of calretinin, HBME‐1, and thrombomodulin for RM/MM was 83%, 79.2%, and 47.2% respectively. The specificity was 88.3%, 21.7%, and 70%, respectively. The expression of E‐cadherin, CEA, MOC‐31, Ber‐EP4, calretinin, and thrombomodulin showed significant difference between ACA and RM/MM (P < 0.01). The reactivity of EMA and Des showed significant difference between RM and MM (P < 0.01). In our opinion, the antibody panel that consists of E‐cadherin, CEA, calretinin, and thrombomodulin should be the best for differential diagnosis between metastatic adenocarcinomas and RM/MM in serous effusions. EMA and Des should be used to differentiate malignant epithelial mesothelioma and reactive mesothelial cells. EMA positive and Des negative favor MM, while Des positive and EMA negative favor RM. Diagn. Cytopathol. 2011.     

Anti-mesothelial markers in sarcomatoid mesothelioma and other spindle cell neoplasms

AIMS: To undertake a comparative evaluation of three antimesothelial markers (thrombomodulin, cytokeratin 5/6 and calretinin) with broad spectrum cytokeratin (AE1/AE3) in differentiating between sarcomatoid mesothelioma and a spectrum of spindle cell neoplasms. METHODS AND RESULTS: Thirty-one malignant sarcomatoid mesotheliomas were studied. Calretinin expression was focally identified in 12 (39%) tumours and thrombomodulin and cytokeratin 5/6 immunoreactivity was seen in nine (29%) cases. In comparison there was strong diffuse cytoplasmic reactivity with the broad spectrum cytokeratin (AE1/AE3) in 24 of 31 (77%) tumours. Thirty mixed spindle cells neoplasms were studied. No calretinin expression was identified in any case. Thrombomodulin immunoreactivity was identified in four (16%) cases (two angiosarcomas, two high-grade sarcomas, not otherwise specified). Cytokeratin 5/6 expression was seen in one high-grade pulmonary sarcoma originally termed malignant fibrous histiocytoma. None of the antimesothelial markers was expressed in the four spindle cell carcinomas studied. In contrast, broad spectrum cytokeratin was diffusely expressed in all four spindle cell carcinomas (three pulmonary, one renal), both synovial sarcomas, both malignant mixed Müllerian tumours, one of three pulmonary leiomyosarcomas and two of nine sarcomas, not otherwise specified. CONCLUSIONS: Immunohistochemistry has a more limited role in the diagnosis and distinction of sarcomatoid mesothelioma from other spindle cell neoplasms. The combination of a broad spectrum cytokeratin with calretinin combines both high sensitivity (77% for AE1/AE3) with high specificity (100% for calretinin) for sarcomatoid mesothelioma and can be diagnostically useful. The mesothelial markers, thrombomodulin and cytokeratin 5/6, are not useful alone in the diagnosis of sarcomatoid mesothelioma as each shows insufficient antibody sensitivity, although together they complement calretinin.     

'Pseudomesotheliomatous' carcinomas of the pleura: a 10-year analysis of cases from the Environmental Lung Disease Research Group, Cardiff

AIMS: To undertake a clinicopathological study of diffuse serosal neoplasms of epithelial histogenesis which clinically and pathologically mimic malignant pleural mesothelioma. METHODS AND RESULTS: Over a 10-year (1990-2000) study period 53 carcinomas mimicking diffuse pleural mesothelioma ('pseudomesotheliomatous' carcinoma) were identified. The study group comprised 50 men and three females, age range 33-77 (median 68) years. In 46 (87%) cases there was a history of smoking and in 40 (76%) cases a history of asbestos exposure. Histologically the pleural 'pseudomesotheliomatous' carcinomas could be divided into two broad groups: primary pulmonary carcinomas with florid pleurotropic growth (n = 47), of which 34 (70%) were adenocarcinomas; and diffuse carcinomatous involvement of the pleura by metastatic tumour (n = 6). This latter group comprised two transitional cell carcinomas of bladder, one renal (clear) cell carcinoma, one ductal pancreatic adenocarcinoma, one prostatic adenocarcinoma and one squamous cell carcinoma of parotid gland origin. Follow-up data were available in 35 cases. Regardless of tumour type, survival was poor (median 8 months) and comparable to diffuse pleural mesothelioma. CONCLUSIONS: Pleural 'pseudomesotheliomatous' carcinomas are uncommon (comprising 6% of referrals), pathologically heterogeneous tumours with poor prognosis. Tissue diagnosis should be obtained in all cases of suspected diffuse pleural neoplasia. By light microscopy and immunophenotype many of the tumours mimicked malignant mesothelioma. In particular, an awareness that all neoplasms exhibiting squamous differentiation may express cytokeratin 5/6 and thrombomodulin is important to prevent misinterpretation. In this respect, calretinin is regarded as the most specific and sensitive mesothelial marker. Misdiagnosis may have medico-legal implications in asbestos-related compensation claims.     

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

We examined 14 spindle cell tumours of the pleura that were sent to a Mesothelioma Panel for re-evaluation after a primary suspicion of mesothelioma. The clinical, histological, immunohistochemical and CGH findings were investigated. Final diagnoses were eight sarcomatoid mesotheliomas (SM) and six non-mesotheliomas: two pulmonary sarcomatoid carcinomas, an epithelioid hemangioendothelioma, a malignant solitary fibrous tumour, a malignant pleural smooth muscle tumour and an extraskeletal osteosarcoma. Seven of the eight SM and two of the other six tumours presented with unilateral pleural effusion, dyspnoea, and chest pain, which are characteristic clinical findings in malignant mesothelioma. No single antibody used in the immunohistochemistry separated SM from other tumour types. The most frequently observed chromosomal losses in SM were 4q, 4p11-p13/p15, 6q and 13. Losses of 4p11-p13/p15 and 4q occurred in combination in four out of five SM with detectable chromosomal changes, but neither was found in any of the other tumours. Gain or high-level amplification of 5p was also common in SM. According to our results and literature, losses at 4p, 4q and 9p and gain at 5p are the chromosomal changes that best differentiate SM from pleural sarcomas and lung carcinomas. CGH analysis may help distinguish a cytokeratin-positive SM from a sarcomatoid carcinoma. Similarly, in the case of a cytokeratin-negative tumour, CGH analysis may disclose chromosomal changes characteristic of sarcomas or mesotheliomas.     

Immunoperoxidase staining of malignant cells in pleural effusions

The indirect immunoperoxidase method was used to detect the presence of carcinoembryonic antigen (CEA), epithelial membrane antigen (EMA), keratin and alpha-1-antichymotrypsin (alpha 1ACT) in cells of pleural fluid sediments from 30 patients with pleural malignancies (18 mesotheliomas and 12 metastatic carcinomas). CEA was negative in all mesotheliomas and positive in all carcinomas but one (an ovarian serous cystadenocarcinoma); alpha 1ACT was positive in mesotheliomas and negative in carcinomas; EMA and keratin were positive in both types of tumor. These data suggest that the use of immunostaining against CEA and alpha 1ACT seems to improve the cytologic differential diagnosis between malignant mesothelioma and metastatic carcinoma in pleural effusions.     

Distinction of mesothelioma from carcinoma in pleural effusions. An immunocytochemical study on routinely processed cytoblock preparations

The study was designed to find out whether the commercially available antibodies BMA 130 c, BMA 120, V 9, KL 1, B 72.3 TAG, HEA 125 and Ber-EP 4 would be of help in distinguishing carcinomas from a mesothelial process (mesothelioma/pleuritis) in pleural effusion specimens routinely processed by the cytoblock method. All of the 20 carcinomas included in the study but also 19 of the 20 mesotheliomas expressed cytokeratin (KL 1), whereas vimentin expression was found in 7 of the 20 carcinomas and 19 of the 20 mesotheliomas. 19 of the 20 carcinomas reacted with the epithelial markers B 72.3 and HEA 125, and 18 of them with Ber-EP 4. In contrast, only a few of the 20 mesotheliomas showed a weak reaction to these markers (1 with HEA 125, 2 with B 72.3, and 3 with Ber-EP 4). BMA-130 c was detected in 10/20 carcinomas but in none of the mesotheliomas. BMA-120 was observed in the effusions from 17/20 mesotheliomas and in cover cells which had undergone reactive changes, but also in 2 cases of ovarian carcinoma. The results show that reaction to the "epithelial markers" B 72.3, HEA 125 and Ber-EP 4 is strongly indicative of carcinoma and not of mesothelioma, whereas a positive reaction with the antibody BMA-120 in the absence of reaction to the epithelial markers makes a mesothelial process very likely. However, immunocytochemical distinction cannot be made as yet between mesothelioma cells and pleuritic cells. If simultaneous positivity for BMA-120 and an "epithelial marker" in a pleural effusion is observed the primary tumor could be an ovarian carcinoma.     

IMMUNOREACTIVITY FOR HEPATOCYTE GROWTH FACTOR/SCATTER FACTOR AND ITS RECEPTOR,met, IN HUMAN LUNG CARCINOMAS AND MALIGNANT MESOTHELIOMAS

Paraffin sections from 29 lung carcinomas (28 primary and 1 metastatic) and 9 pleural malignant mesotheliomas were immunostained with antisera to human hepatocyte growth factor/scatter factor (HGF/SF) and its receptor, met. For HGF/SF, immunoreactivity was demonstrated in all 9 mesotheliomas, 9 of 12 adenocarcinomas, and 7 of 10 squamous cell carcinomas. None of seven cases of small cell anaplastic carcinoma was positive. The adenocarcinomas frequently showed enhanced luminal staining, suggesting possible secretion of HGF/SF, and this pattern of staining was also seen occasionally in bronchial epithelium adjacent to the tumour. Stromal fibroblasts also showed immunoreactivity for HGF/SF in 6/8 cases of mesothelioma but in only 3/12 adenocarcinomas, 1/10 squamous cell carcinomas, and 1/4 small cell anaplastic carcinomas. All tumours stained for met, usually strongly. The staining was mainly cytoplasmic in nature, but some plasma membrane staining was usually evident. Adenocarcinomas showed strong luminal membrane staining, as did adjacent, histologically normal bronchial epithelium. This study demonstrates the presence of HGF/SF and met in most of the tumour types described, particularly mesotheliomas, and suggests that the HGF/SF/met signalling system may play a role in the development of these tumours, either by autocrine or by paracrine mechanisms.     

The diagnostic utility of immunohistochemistry in distinguishing between mesothelioma and renal cell carcinoma: a comparative study

Both mesotheliomas and renal cell carcinomas can present a wide variety of morphological patterns. Because of this, renal cell carcinomas that metastasize to the pleura and lung may be confused with mesotheliomas. The aim of the present study was to compare the value of the various immunohistochemical markers currently available for the diagnosis of mesothelioma and renal cell carcinoma. A total of 48 mesotheliomas (40 epithelioid, 8 sarcomatoid), and 48 renal cell carcinomas (24 conventional, 12 chromophobe, 8 papillary, 4 sarcomatoid) were investigated for the expression of the following markers: calretinin, mesothelin, cytokeratin 5/6, WT1, thrombomodulin (TM), N-cadherin, CD15 (leu-M1), MOC-31, Ber-EP4, BG-8 (Lewis(y)), CD10, renal cell carcinoma marker (RCC Ma), carcinoembryonic antigen (CEA), and B72.3. All (100%) of the epithelioid mesotheliomas reacted for calretinin, mesothelin, and cytokeratin 5/6; 93% for WT1; 78% for TM; 75% for N-cadherin, 48% for CD10, 15% for Ber-EP4, 8% for MOC-31, 8% for RCC Ma, 5% for BG-8, and none for CEA, B72.3, or CD15. Of the sarcomatoid mesotheliomas, 88% expressed calretinin, 75% N-cadherin, 38% CD10, and 13% each expressed cytokeratin 5/6, WT1, and TM. All of the remaining markers were negative. Among the RCCs, 81% expressed CD10, 75% N-cadherin, 63% CD15, 50% RCC Ma, 50% MOC-31, 42% Ber-EP4, 8% BG-8, and 2% TM. The remaining markers were negative. The results indicate that calretinin, mesothelin, and cytokeratin 5/6 are the best positive mesothelioma markers for differentiating epithelioid mesotheliomas from renal cell carcinomas. The best discriminators among the antibodies considered negative markers for mesothelioma are CD15, MOC-31, and RCC Ma. An accurate differential diagnosis can be reached with the use of any 2 of the 3 recommended positive markers, which should be selected based on availability and on which ones yield the best staining results in a given laboratory. One of the recommended negative markers may be added to the panel if deemed necessary. If confirmation of renal origin is needed, RCC Ma could be useful. Calretinin is the only marker that appears to have any utility in distinguishing between sarcomatoid mesotheliomas and sarcomatoid renal cell carcinomas.     

Histologic distinction between malignant mesothelioma,benign pleural lesion and carcinoma metastasis

Summary Thirty men and 7 women with malignant mesothelioma seen at the Free University Hospital from 1st January 1960 until 1st July 1981 were reviewed.The histological, histochemical and morphometrical findings are reported. These findings are compared with 25 cases of pleural metastatic carcinoma and 25 cases of reactive pleural lesions.Fourty-nine percent of malignant mesotheliomas produced hyaluronic acid, however all cases of pleural metastatic carcinomas failed to produce this substance. All cases of malignant mesothelioma were D-PAS negative while 15 cases of pleural metastatic carcinoma showed reactivity to D-PAS. All cases of malignant mesothelioma and 9 cases of metastases were CEA negative.To distinguish malignant mesothelioma from metastases it is advisable to perform the D-PAS staining first. If it is negative mesothelioma can be confirmed by showing hyaluronic acid activity. A positive CEA staining rules out mesothelioma. In our study it was shown that with these methods 18 of 37 mesotheliomas could be identified with certainty, and 22 of the 25 carcinoma metastases.Morphometrically the malignant mesotheliomas could not be distinguished from the metastases, however the reactive pleural lesions had smaller nuclei than the malignant cells with mean values below 30 mu². In the malignant cases these values had a range from 36 to 101 mu².In distinguishing between reactive pleural lesions and malignant mesothelioma the production of hyaluronic acid points to the malignant character of the lesion.Thus histochemistry and immunostaining are important in the distinction of malignant mesothelioma from metastases, while the value of morphometry lies mainly in the separation of reactive lesions from malignant mesothelioma.     

Immunohistochemical differentiation of sarcomatoid mesotheliomas from other spindle cell neoplasms

A sizable proportion of pleural malignant mesotheliomas are sarcomatoid (22%) or biphasic (24%) and may need to be distinguished from other spindle cell neoplasms that occur as primary or metastatic tumors of the chest wall or lungs. To determine the utility of immunohistochemistry in the differentiation of sarcomatoid malignant mesotheliomas from other spindle cell neoplasms, the authors studied the immunostaining patterns of nine antibodies in four sarcomatoid mesotheliomas, one desmoplastic mesothelioma, two epithelial mesotheliomas, four spindle cell squamous carcinomas, and eight sarcomas of various differentiation. Three of the four sarcomatoid mesotheliomas and the desmoplastic mesothelioma had positive results for cytokeratin, which distinguishes them from sarcomas but not from spindle cell squamous carcinomas. The immunostaining pattern of 14 examples of benign spindle cell mesothelial proliferation was similar to that of the sarcomatoid mesotheliomas, which supports the theory that these tumors are mesothelial in origin. Although other antibodies occasionally may be helpful, depending on the differentiation of the sarcoma, cytokeratin immunostaining appears to be the best method to discriminate sarcomatoid mesotheliomas from sarcomas.     

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.     

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.     

Value of mesothelial and epithelial antibodies in distinguishing diffuse peritoneal mesothelioma in females from serous papillary carcinoma of the ovary and peritoneum

AIMS: To evaluate the role of mesothelial markers (calretinin, thrombomodulin, cytokeratin 5/6, and CD44H) and carcinoma markers (polyclonal and monoclonal carcinoembryonic antigen, Leu-M1, CA-125 and Ber-EP4) in distinguishing diffuse peritoneal malignant mesothelioma from primary serous papillary adenocarcinoma of the ovary and peritoneum. METHODS AND RESULTS: Paraffin-embedded formalin-fixed blocks from 32 diffuse peritoneal mesotheliomas of epithelial subtype (all females), 20 serous papillary ovarian carcinomas and three primary peritoneal serous papillary carcinomas were studied. Calretinin and Ber-EP4 appeared to be the best positive mesothelial and carcinoma marker, respectively. Nuclear calretinin expression was identified in 28 of 32 malignant mesotheliomas with no nuclear immunoreactivity in the cohorts of serous papillary ovarian and peritoneal carcinomas, thus yielding 88% sensitivity and 100% specificity. Ber-EP4 showed 95% sensitivity and 91% specificity for serous papillary ovarian carcinoma. Thrombomodulin, cytokeratin 5/6 and CD44H immunoreactivities were seen in 18 (56%), 17 (53%) and 15 (47%) of peritoneal mesotheliomas, respectively, and in six (30%), five (25%) and five (25%) of the ovarian tumours, respectively. None of the three primary peritoneal serous papillary carcinomas expressed calretinin, thrombomodulin, cytokeratin 5/6 or CD44H. Polyclonal and monoclonal CEA, and Leu-M1 were expressed by two (10%), one (5%) and seven (35%) serous papillary ovarian carcinomas, respectively. None of the serous papillary peritoneal carcinomas expressed polyclonal CEA, monoclonal CEA or Leu-M1. CA-125 was positive in 19 (95%) and two (67%) ovarian and peritoneal carcinomas, respectively, and in eight (25%) peritoneal mesotheliomas. CONCLUSIONS: Calretinin and Ber-EP4 are useful discriminant markers in distinguishing peritoneal mesothelioma in women from serous papillary ovarian and peritoneal carcinoma. The other mesothelial markers (thrombomodulin, cytokeratin 5/6, and CD44H) and carcinoma markers (polyclonal and monoclonal CEA, and Leu-M1) yielded a too low sensitivity for practical use.