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

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

Value of mesothelin immunostaining in the diagnosis of mesothelioma.

Mesothelin is a cell surface antigen of unknown function that is strongly expressed in mesothelial cells. Although it was reported in 1992 that immunostaining with the K1 anti-mesothelin antibody could be very useful in distinguishing between epithelioid mesotheliomas and pulmonary adenocarcinomas, no further studies have been published on the value of this marker in the diagnosis of mesotheliomas. To determine whether mesothelin can assist in discriminating epithelioid mesotheliomas from lung adenocarcinomas or from other carcinomas metastatic to the serosal membranes, 55 mesotheliomas (44 epithelioid, 3 biphasic, and 8 sarcomatoid), 48 carcinomas of the lung (31 adenocarcinomas, 17 squamous carcinomas), and 86 nonpulmonary adenocarcinomas (14 ovary, 5 peritoneum, 9 endometrium, 11 pancreas, 4 stomach, 16 colon, 12 breast, 9 kidney, 4 thyroid, and 2 prostate) were investigated for mesothelin expression using the recently available 5B2 anti-mesothelin monoclonal antibody. Reactivity was obtained in all 44 (100%) of the epithelioid mesotheliomas, 12 (39%) of the lung adenocarcinomas, and 42 (49%) of the nonpulmonary adenocarcinomas (14 [100%] ovary; 5 [100%] peritoneum; 6 [67%] endometrium; 10 [91%] pancreas; 2 [50%] stomach; 5 [31%] colon; and in none [0] of the breast, kidney, thyroid, or prostate). Three (18%) of the squamous carcinomas of the lung, but none of the sarcomatoid mesotheliomas, exhibited positivity for this marker, nor was any reactivity seen in the spindle cell component of the biphasic mesotheliomas. It is concluded that despite the low specificity of mesothelin for discriminating between epithelioid mesotheliomas and adenocarcinomas, immunostaining for this marker may have some utility in those instances in which the results obtained with the standard panel of immunohistochemical markers used for the diagnosis of mesotheliomas are equivocal. Because mesothelin is a highly sensitive positive marker for epithelioid mesotheliomas, a negative staining for this marker is an indication against such a diagnosis; however, because of its limited utility, it is not recommended for inclusion in the standard panel of immunohistochemical markers used in the distinction between mesotheliomas and adenocarcinomas.     

D2-40 and podoplanin are highly specific and sensitive immunohistochemical markers of epithelioid malignant mesothelioma

Recent investigations have shown that podoplanin and the D2-40 monoclonal antibody, which reacts with an oncofetal antigen present in fetal germ cells, are highly reliable lymphatic endothelial markers. The observation that both of these markers are also expressed in normal and reactive mesothelial cells prompted an investigation into their potential value in the diagnosis of mesotheliomas. To determine whether podoplanin and D2-40 had any use in the diagnosis of these tumors, 40 mesotheliomas (29 epithelioid, 5 biphasic, and 6 sarcomatoid), 34 carcinomas of the lung (24 adenocarcinomas, 10 squamous carcinomas), 80 nonpulmonary adenocarcinomas (17 ovary, 10 breast, 10 colon, 10 kidney, 5 endometrium, 5 stomach, 5 pancreas, 5 prostate, 3 thyroid), 12 synovial sarcomas (6 biphasic and 6 monophasic), 5 angiosarcomas, and 2 adenomatoid tumors were immunostained with a monoclonal antibody to podoplanin and with the D2-40 antibody. Reactivity for both D2-40 and podoplanin was obtained in 25 (86%) of the 29 epithelioid mesotheliomas but in none of the carcinomas or sarcomatoid mesotheliomas. Positivity for D2-40 and podoplanin was also seen in the epithelioid components of 4 of 5 biphasic mesotheliomas and 4 of 6 synovial sarcomas, whereas the spindle cell components of these tumors were negative as were the monophasic synovial sarcomas. Two (40%) of the 5 angiosarcomas expressed these markers, thus confirming previous reports suggesting that some angiosarcomas may have lymphatic endothelial differentiation. Both of the adenomatoid tumors were also positive for D2-40 and podoplanin, a finding which provides further support for the mesothelial derivation of these tumors. It is concluded that, because of their high specificity and sensitivity for epithelioid mesotheliomas, D2-40 and podoplanin are very useful markers for the diagnosis of these tumors. When compared with the other markers that are currently available, in my opinion, they appear to be the best.     

E-cadherin,E-selectin and vascular cell adhesion molecule: immunohistochemical markers for differentiation between mesothelioma and metastatic pulmonary adenocarcinoma?

Pleural mesotheliomas, especially pure epithelioid mesotheliomas, may histologically be easily confused with peripheral pulmonary adenocarcinomas or pleural carcinosis. As there is no specific antibody for mesotheliomas, today a panel of immunohistochemical markers is used for the differential diagnosis of these two tumour entities. In search of further significant antibodies for application onto formalin-fixed, paraffin-embedded tissue, we immunohistochemically investigated the expression pattern of three adhesion molecules: vascular cell adhesion molecule (VCAM), E-selectin and E-cadherin. A comparatively large number of 44 mesotheliomas (15 epithelioid, 15 biphasic, 14 sarcomatoid) and 18 peripheral pulmonary adenocarcinomas were analysed. While for these two tumour entities there were no significant differences of the staining patterns for VCAM and E-selectin, there were significant differences in the expression of E-cadherin: while nearly all adenocarcinomas stained positively, there was almost no staining reaction of the mesotheliomas. Therefore, E-cadherin -- in contrast to E-selectin and VCAM -- appears to be a further relevant immunohistochemical marker for the distinction between adenocarcinomas and mesotheliomas.     

Anti-cytokeratin 5/6: a positive marker for epithelioid mesothelioma

Aims : Previous studies using frozen material have suggested that cytokeratin 5 is expressed by pleural mesothelioma but not by adenocarcinoma. In the present study, reactions for cytokeratins 5 and 6 were investigated in 33 pleural mesotheliomas and 27 secondary adenocarcinomas of the pleura using formalin-fixed, paraffin-embedded material and a commercially available antibody (anti-cytokeratin 5/6). Methods and results : All of the adenocarcinomas originated in the peripheral lung. The epithelioid component of the mesotheliomas gave a strongly positive reaction; the reaction in sarcomatoid or desmoplastic areas was absent or weak. Twenty-two of the adenocarcinomas were negative, in four there was a weak, equivocal reaction, and in one there was patchy positivity. Conclusions : We conclude that this antibody is potentially a useful positive marker for the identification of the epithelioid variant of mesothelioma in formalin-fixed and paraffin-embedded material.     

Membranous HEG1 expression is a useful marker in the differential diagnosis of epithelioid and biphasic malignant mesothelioma versus carcinomas

Sialylated HEG1 has been reported as a highly specific and sensitive mesothelioma marker but a comprehensive evaluation of its expression in carcinomas in different organs, various sarcomas and reactive mesothelial proliferations has not been reported. The aim of this study was to evaluate the clinical applicability of HEG1 as a marker in the diagnosis of mesothelioma. HEG1 immunoreactivity was evaluated in whole sections of 122 mesotheliomas, 75 pulmonary carcinomas, 55 other carcinomas, 16 mesenchymal tumors, and 24 reactive mesothelial proliferations and in tissue microarrays containing 70 epithelioid (EM), 36 biphasic (BM), and 2 sarcomatoid mesotheliomas (SM). In whole sections and tissue microarrays, respectively, membranous HEG1 was expressed in 93.0% and 85.5% of EM, 81.3% and 69.4% of BM, 0% and 0% of SM. HEG1 was not expressed in pulmonary adenocarcinomas. HEG1 was expressed as cytoplasmic immunoreactivity in pulmonary squamous cell carcinomas (21.7%). Membranous HEG1 staining was seen in ovarian carcinomas (66.7%), thyroid carcinomas (100%), reactive conditions (16.7%), and mesenchymal tumors (18.8%). The sensitivity of membranous HEG1 expression to distinguish EM/BM from all carcinomas was 88.8%. The specificity for the differential diagnosis between EM/BM and all carcinomas and pulmonary carcinomas was 92.3% and 98.7%, respectively.     

Morphologische Diagnostik maligner Pleuramesotheliome

The World Health Organization (WHO) classification differentiates between pleural tumors of mesothelial and mesenchymal origin as well as lymphoproliferative disorders, with malignant mesotheliomas forming the most common pleural primary tumor. Histologically, epithelioid (40–60?%), sarcomatoid (20–40?%), and biphasic mesotheliomas (20–40?%) are distinguished. The certain morphological diagnosis of a malignant pleural mesothelioma requires the establishment of mesothelial differentiation by means of an appropriate panel of antibodies to exclude pleural dissemination of a pulmonary or extrapulmonary epithelial malignancy and also requires the establishment of at least focal invasive growth to distinguish from reactive mesothelial proliferation. The exclusion of a malignant pleural mesothelioma may induce further differential diagnostic considerations, e. g. concerning the assignment to a certain primary tumor after the establishment of carcinomatous pleuritis.     

Assessment of cell cycle state may facilitate the histopathological diagnosis of malignant mesothelioma

AIMS: The differentiation of benign pleural conditions from malignant mesothelioma may be difficult, especially with a small biopsy. We have tested the hypothesis that assessment of the cell cycle status is of value in the histopathological diagnosis of such biopsies, by comparing 33 malignant mesotheliomas with 36 cases of reactive mesothelial hyperplasia and reactive pleural fibrosis. METHODS AND RESULTS: Biopsies were investigated for proliferative status by immunostaining for a novel antibody, MCM2, all of which showed nuclear expression of MCM2 at higher frequency than Ki67 (P < 0.0001). Counts in areas of maximum tumour staining showed significantly higher labelling indices (LIMax) in epithelioid and sarcomatoid mesotheliomas compared with reactive mesothelial hyperplasia and reactive pleural fibrosis (P < 0.0001 for both). Average counts (LIAve) revealed a significant increase in epithelioid mesothelioma compared with reactive mesothelial hyperplasia (P < 0.0001). CONCLUSION: We consider MCM2 to be a useful adjunct in the differential diagnosis of malignant mesothelioma.     

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.     

Unusual intraparenchymal growth patterns of malignant pleural mesothelioma

AIMS: Malignant pleural mesothelioma is known to mimic morphologically a number of diverse reactive and neoplastic conditions. We describe three unusual intraparenchymal growth patterns of malignant mesothelioma seen in a series of 200 malignant pleural mesotheliomas. The diagnostic pitfalls associated with these findings are described and their potential medico-legal implications are highlighted. METHODS AND RESULTS: The study group comprised 200 malignant pleural mesotheliomas. In each case diagnosis was morphologically confirmed with ancillary immunohistochemistry using a broad panel of both mesothelial and epithelial markers. The patterns of intraparenchymal growth were documented and grouped as: direct subpleural; lymphangitic; and other. The 200 malignant pleural mesotheliomas comprised 118 epithelioid, 57 biphasic and 25 sarcomatoid, subtyped according to the WHO classification. Direct subpleural invasion was seen in 42 cases, lymphangitic spread in 27 cases. Other less well-defined intraparenchymal patterns included three sarcomatoid subtype malignant mesotheliomas exhibiting an intra-alveolar growth pattern mimicking epithelioid haemangioendothelioma. One epithelioid subtype malignant mesothelioma contained an intraparenchymal tumour nodule microscopically comprising lepidic spread of neoplastic cells over maintained alveolar structures mimicking bronchioloalveolar carcinoma. One epithelioid subtype malignant mesothelioma morphologically had areas in which alveoli were distended by discohesive epithelioid neoplastic cells with no interstitial invasion. The appearances mimicked desquamative interstitial pneumonia. Immunohistochemistry played an important role in the definitive diagnosis of each unusual parenchymal tumour deposit. In 126 malignant mesotheliomas no invasion of the subjacent lung parenchyma was identified. CONCLUSIONS: An awareness of the unusual parenchymal growth pattern in malignant mesothelioma is important to prevent misdiagnosis of other entities. In the medico-legal setting, the presence of epithelioid haemangioendothelioma or bronchioloalveolar carcinoma (in the absence of asbestosis) may be deemed to impact upon the patient's anticipated life expectancy and thereby would decrease the compensation settlement.     

NCAM (neural cell adhesion molecules) expression in malignant mesotheliomas

Neural cell adhesion molecules (NCAM) are adhesion molecules expressed by neural and neuroendocrine tumors and a few biphasic tumors such as synovialosarcomas and breast phyllode tumors. To investigate NCAM expression in mesotheliomas, we studied 26 cases of epithelioid (n = 12), biphasic (n = 11), and sarcomatoid (n = 3) malignant mesotheliomas (MM), in comparison with normal mesothelium, and 50 primary non-small cell lung carcinomas (NSCLC) (25 adenocarcinomas [ADC] and 25 squamous cell carcinomas [SCC]), using electron microscopy as a gold standard for recognition of MM. NCAM reactivity using 123C3 antibody was compared with that of NE markers such as chromogranin A and synaptophysin. Although normal mesothelium remains negative, NCAM was expressed in 19 of 26 MM (73%) with a membranous staining on frozen or paraffin sections. In 6 of 12 epithelioid MM, the tumor cells expressed NCAM, whereas in 5 cases stromal fibroblasts showed a strong but focal staining. In 11 biphasic MM, 4 presented an NCAM reactivity of both epithelioid and spindle cell components, whereas in 7, only fusiform component was NCAM positive. Two of 3 sarcomatoid MM showed an NCAM expression. Chromogranin expression was never seen, whereas synaptophysin was noticed in 2 cases. No case of NSCLC showed membranous 123C3 staining, whereas 2 ADC weakly expressed synaptophysin. We conclude that NCAM expression in MM is reminiscent of its expression in mesoderm during fetal life and consistent with that reported in other biphasic tumors. These data show that NCAM expression occurs in 73% of MM, highly exceeding that observed in lung cancer.     

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.     

Diagnostic utility of D2-40 and podoplanin in effusion cell blocks

The distinction between malignant mesothelioma and adenocarcinoma is a diagnostic challenge in cytologic specimens of effusion fluids. As for today, no single antibody has demonstrated absolute sensitivity or specificity for Mesothelioma. D2-40 and podoplanin have recently been recognized to stain mesothelial cells. Our aim for this study was to evaluate the utility of these two markers as indicators of mesothelial cells using cell blocks by comparison with two other established mesothelial markers. A total of 40 cell blocks of effusion fluids including cases of epithelioid mesotheliomas, metastatic carcinomas and benign cases with reactive mesothelial cells were selected. A panel of immunostains including D2-40, podoplanin, CK5, and calretinin was performed. D2-40 and podoplanin were positive in 100% of mesothelioma cases in comparison to metastatic adenocarcinoma cases where the positivity was 0%. It is concluded that D2-40 and podoplanin are very useful markers for mesotheliomas. Since these markers are extremely helpful in differentiating epithelioid mesothelioma from metastatic adenocarcinoma, they shall be a valuable addition to the battery of markers used to differentiate the two entities.     

Pleural malignant mesothelioma with invasive micropapillary component and its association with pulmonary metastasis

The micropapillary pattern (characterized by papillary structure with tufts lacking a central fibrovascular core) is a predictor of aggressive carcinoma. The purpose of the present study was to review 34 pleural malignant mesotheliomas (21 epithelioid, five sarcomatoid, seven biphasic and one lymphohistiocytoid), with special reference to the presence of invasive micropapillary component. Two invasive micropapillary pattern‐positive tumors were identified. The invasive micropapillary pattern was seen to have a focal distribution in 15–20% of the tumor tissues. The majority of the invasive micropapillary clusters expressed MUC1 along the outer cell surface. Analysis of pleural malignant mesotheliomas with epithelioid features and with or without invasive micropapillary pattern (21 epithelioid and seven biphasic subtypes) indicated pulmonary micrometastases in only the invasive micropapillary‐positive tumors (P < 0.015), and the spread was probably via the lymphatics. Lymphatic involvement (confirmed on immunohistochemistry with D2‐40 antibody) and lymph node metastasis were found in both of the invasive micropapillary‐positive tumor patients, whereas they were noted in only one of 10 (10%, P < 0.046) and three of nine (30%) invasive micropapillary‐negative patients. To the authors’ knowledge this is the first study to indicate the presence of invasive micropapillary component in pleural malignant mesothelioma. This component can predict more aggressive lymphatic spread, similar to that of carcinomas in other organs with micropapillary pattern.     

Distinctive microvillous brush border staining with HBME-1 distinguishes pleural mesotheliomas from pulmonary adenocarcinomas

HBME-1 is an antimesothelial monoclonal antibody that recognises an unknown antigen on microvilli of mesothelioma cells. The aim of this study was to evaluate the staining pattern with respect to antibody dilution, cellular distribution and intensity of immunohistochemical staining with HBME-1 in pleural mesotheliomas compared with pulmonary adenocarcinomas. A total of 27 pulmonary adenocarcinomas and 26 mesotheliomas were stained with commercially available HBME-1 at various antibody dilutions and evaluated for the site (membranous, +/- microvillous brush border or cytoplasmic), intensity and percentage of cells staining. On light microscopy, 23 mesotheliomas showed distinctive microvillous brush border staining with HBME-1 (three mesotheliomas--two sarcomatoid and one poorly differentiated--were negative). Twenty-five adenocarcinomas showed membranous +/- cytoplasmic staining but lacked the distinctive microvillous brush border staining. In a subgroup of tumours studied by electron microscopy following immunogold labelling by HBME-1, all of 16 mesothelioma cases showed strong immunogold labelling in the membranes of the long microvilli. In contrast, the 12 cases of pulmonary adenocarcinomas showed minimal labelling in the membranes of the short microvilli, but staining was seen within vesicles, often near the surface of the cells. This study shows that the presence of a distinctive microvillous brush border by immunohistochemical staining with HBME-1 allows distinction between pleural mesotheliomas and pulmonary adenocarcinomas (sensitivity of 88%, specificity of 100%). The difference in the ultrastructural distribution of immunogold labelling with HBME-1 between mesotheliomas and adenocarcinomas underscores the light microscopy findings.