间皮相关抗体在胸膜恶性间皮瘤和胸膜转移癌鉴别诊断中的作用

目的　探讨calretinin、CK5 / 6、mesothelialcell(MC)、CEA和vimentin在胸膜恶性间皮瘤及胸膜转移性肺腺癌中的表达及其在鉴别诊断中的作用。方法　用免疫组化EnVision二步法检测 13例胸膜恶性间皮瘤和 13例胸膜转移性肺腺癌中的calretinin、CK5 / 6、MC、CEA、vimentin的表达情况。结果　calretinin、CK5 / 6、CEA在恶性间皮瘤与胸膜转移性肺腺癌中表达差异有显著性 (P <0 0 5 )。MC、vimentin在恶性间皮瘤和胸膜转移性肺腺癌中表达差异无显著性 (P >0 0 5 )。结论　间皮相关抗体calretinin、CK5 / 6及癌抗体CEA对鉴别胸膜恶性间皮瘤及胸膜转移性肺腺癌有诊断价值。     

Utility of D2-40, a novel mesothelial marker, in the diagnosis of malignant mesothelioma.

Although immunohistochemistry has proven to be valuable in the differentiation of epithelioid mesothelioma from pulmonary or metastatic adenocarcinoma, no single antibody has demonstrated absolute sensitivity or specificity in making this distinction. Using immunohistochemical analysis with D2-40, a recently available monoclonal antibody that has been used as a lymphatic endothelial marker, we examined 53 cases of mesothelioma, 28 cases of reactive pleura, 30 cases of pulmonary adenocarcinoma, 35 cases of renal cell carcinoma, 26 cases of ovarian serous carcinoma, 16 cases of invasive breast carcinoma, 11 cases of prostatic adenocarcinoma, and seven cases of urothelial carcinoma. In addition, immunohistochemistry using calretinin, cytokeratin 5/6, and WT1 was performed on all cases of mesothelioma, pulmonary adenocarcinoma, ovarian serous carcinoma, and renal cell carcinoma. Predominantly, membranous D2-40 immunoreactivity was present in 51 of 53 (96%) mesotheliomas, 27 of 28 (96%) cases of reactive pleura, and 17 of 26 (65%) ovarian serous carcinomas; membranous staining was not seen in any other tumors examined. Compared to other immunohistochemical markers of mesothelioma, D2-40 was as sensitive as calretinin and more sensitive than cytokeratin 5/6 and WT1. We conclude that D2-40 immunoreactivity is sensitive for cells of mesothelial origin, and may be useful in the differential diagnosis of epithelioid malignant mesothelioma vs adenocarcinoma.     

Immunohistochemical distinction of malignant mesothelioma from pulmonary adenocarcinoma with anti-surfactant apoprotein, anti-Lewisa, and anti-Tn antibodies

Nine cases of malignant mesothelioma of pure epithelial and biphasic types (five pleural, three peritoneal, and one pericardial mesotheliomas), seven cases of benign adenomatoid tumor of the uterus, and 21 cases of peripheral pulmonary adenocarcinoma of non-mucus-producing type were examined immunohistochemically for expression of keratin, vimentin, carcinoembryonic antigen (CEA), surfactant apoprotein, Lewis blood group antigens, and Tn antigen. The majority (78%) of the malignant mesotheliomas expressed keratin, but CEA and surfactant apoprotein were not detected in any mesotheliomas. On the other hand, pulmonary adenocarcinomas expressed not only keratin (100%), but also CEA (62%) and surfactant apoprotein (62%). The expression of Lewisa blood group antigen and Tn antigen was detected in 76% and 62% of the pulmonary adenocarcinomas, respectively, but only one mesothelioma was stained for Lewisa antigen. This study reveals that the majority of malignant mesotheliomas can be distinguished from pulmonary adenocarcinomas by immunohistochemcial staining for CEA, surfactant apoprotein, Lewisa antigen, and Tn antigen. Immunohistochemically, adenomatoid tumors behaved similarly to malignant mesotheliomas.     

Differences in lectin binding of malignant pleural mesothelioma and adenocarcinoma of the lung.

In order to differentiate between malignant pleural mesothelioma and adenocarcinoma of the lung, the glycoconjugate profiles of 6 reactive mesothelial lesions, 23 mesotheliomas (17 epithelial, 1 desmoplastic, 2 biphasic, and 3 fibrous types), and 28 well-differentiated pulmonary adenocarcinomas were evaluated with the use of 8 lectins in addition to anti-carcinoembryonic, anti-keratin and anti-epithelial membrane antigen. Formalin-fixed, paraffin-embedded tissues were stained with the avidin-biotin peroxidase complex method. Reactions of wheat germ (WGA) and peanut (PNA) agglutinin with neuraminidase treatment lectins were positive in 5 of 6 (83%) and 3 of 6 (50%) cases, respectively, in reactive mesothelial lesions. Thirteen of 23 (57%) malignant mesotheliomas of the pleura showed a positive reaction for WGA and PNA with neuraminidase treatment; other lectins were low-positive, below 9%. In contrast, pulmonary adenocarcinomas showed positive reactions in 27 of 28 cases (96%) for PNA, 26 of 28 (93%) for Ricinus communis (RCA-I), 25 of 28 (89%) for WGA, and 22 of 28 (79%) for succinylated WGA (SucWGA). The findings suggest that malignant pleural mesothelioma and pulmonary adenocarcinoma have consistent and distinct glycoconjugate profiles, and that stains for RCA-I and SucWGA may be useful for differential diagnosis.     

'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.     

Synchronous pulmonary carcinoma and pleural diffuse malignant mesothelioma

Synchronous pulmonary carcinoma and pleural diffuse malignant mesothelioma is rare. Cases from the archives of 2 large referral centers were reviewed to identify cases of synchronously occurring pulmonary carcinoma and pleural diffuse malignant mesothelioma. Three cases of synchronous pulmonary carcinoma and pleural diffuse malignant mesothelioma were identified from more than 16,000 pleuropulmonary cases and were reviewed for demographic, clinical, radiographic, histologic, and immunohistochemical findings. The patients were men who were 63, 67, and 77 years old. Two had positive smoking histories; the smoking history of the other patient is unknown. One patient had a positive history of asbestos exposure; one patient had no history of asbestos exposure; and one patient's history of asbestos exposure is unknown. The patients underwent surgery for treatment of adenocarcinoma that was diagnosed preoperatively. Two of the adenocarcinomas were of a predominantly bronchioloalveolar pattern. No diffuse malignant mesothelioma was identified preoperatively. Diffuse malignant mesothelioma was suspected on the basis of pleural involvement by tumor with histology differing from that of the adenocarcinoma. Tumor immunostaining supported the diagnoses. The average survival after diagnosis was 6 weeks or less. In summary, the paucity of cases at 2 large referral centers and the paucity of cases reported in the English language literature highlights the rarity of synchronous pulmonary carcinoma and pleural diffuse malignant mesothelioma. These synchronous neoplasms occur in patients who have risk factors for both neoplasms independently. Length of survival following diagnosis is bleak.     

一组细胞角蛋白抗体在胸腹腔积液中的表达及其鉴别诊断价值

目的:探讨一组细胞角蛋白抗体在胸腹腔积液中的表达情况及其临床应用价值。方法:选取72例胸腹腔积液标本,其中腺癌30例,鳞癌22例,反应增生性间皮细胞22例,应用细胞免疫化学SP法检测细胞角蛋白CK(AE1/AE3)、细胞角蛋白5/6(CK5/6)、细胞角蛋白18(CK18)的表达。结果:三种抗体在反应增生性间皮细胞、腺癌细胞、鳞癌细胞中阳性率分别是CK(AE1/AK3):10.0%,73.3%,68.2%;CK5/6:60.0%,6.7%,77.3%;CK18:0,80.0%,4.5%。组合CK(AE1/AE3)(-)、CK5/6(+)、CK18(-)检测间皮细胞的敏感性为93.3%,特异性为80.2%;CK5/6(-)、CK18(+)检测腺癌细胞的敏感性为84.7%,特异性为93.6%;CK(AE1/AE3)(+)、CK5/6(+)、CK18(一)检测鳞癌细胞的敏感性为86.4%,特异性为92.8%。结论:多项细胞角蛋白联检提高了诊断反应增生性间皮细胞、腺癌细胞、鳞癌细胞的敏感性和特异性,可辅助细胞形态学对于良恶性胸腹腔积液的鉴别诊断。     

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.     

Podoplanin is a useful marker for identifying mesothelioma in malignant effusions

The diagnosis of malignant mesothelioma in serosal effusions continues to be a major challenge because some of its cytomorphological features closely resemble adenocarcinomas. Immunohistochemistry is a valuable tool in the differentiation of epithelioid mesothelioma from metastatic adenocarcinomas. However, no single antibody has demonstrated absolute sensitivity or specificity. In this study, we evaluated the value of immunostaining pattern for podoplanin to differentiate mesothelioma from adenocarcinomas of various origins. Cell blocks from previously collected paraffin‐embedded cell blocks of 86 effusions (18 mesothelioma, 35 reactive mesothelium, 9 breast adenocarcinoma, 14 ovarian adenocarcinoma, and 10 lung adenocarcinoma) were retrieved from the file of the Department of Pathology at University of Michigan and Lund University in Sweden and were used for the study. Slides prepared from the cell blocks were stained for podoplanin. The percentage of immunostained cells was recorded as follows: 1+ (5–25%), 2+ (26–50%), and 3+ (>50%). A stain result involving <5% of cells was considered negative. The intensity of positive results was evaluated as strong, moderate, or weak. Podoplanin is expressed in 94% of malignant mesothelioma cases (17/18), 97% (30/31) of cases of reactive mesothelial, 0% of lung adenocarcinoma cases (0/9), 0% of breast adenocarcinoma (0/9), and 7% of ovarian adenocarcinoma (1/14). All positive cases of malignant mesothelioma and reactive mesothelium showed strong membranous reactivity to podoplanin. The one positive case of ovarian adenocarcinoma showed a weak membranous podoplanin immunostaining. On the basis of our results and published data, we believe that membranous podoplanin immunoreactivity, in conjunction with calretinin, would be more specific than CK5/6 and WT‐1 in differentiating epithelioid malignant mesothelioma from adenocarcinoma of the lung, breast, and ovary. Diagn. Cytopathol. 2010. © 2010 Wiley‐Liss, Inc.     

TTF-1在肺腺癌中的表达及其诊断意义

目的：评价甲状腺转录因子－1（TTF－1）在鉴别肺原发性腺癌与转移性腺癌中的临床病理应用价值。方法：20例肺原发性腺癌：10例高分化，包括3例乳头状、3例腺泡状、3例混合型腺癌和1例细支气管肺泡癌；10例低分化，包括4例黏液腺癌（其中1例为印戒细胞癌）和6例混合型腺癌。另选20例的胃肠道及卵巢腺癌，免疫组化应用TTF－1抗体。结果：95％的肺原发性腺癌表达TTF－1，而胃肠道及卵巢腺癌完全不表达。结论：对于确定肺原发或转移性腺癌的病理诊断。TTF－1是一个有用的特异性抗体，特别是在体积较小的肺活检标本或原发灶不明而仅有肺内转移时。     

The diagnostic utility of D2-40 for malignant mesothelioma versus pulmonary carcinoma with pleural involvement

Differentiating malignant mesothelioma (MM) from pulmonary carcinoma in pleural fluid cytology can be challenging. Recent studies have suggested that D2-40, a novel lymphatic marker, may be a useful marker for mesothelial differentiation in surgical specimens. However, there are no available data regarding its utility in effusion cytology specimens. We investigated the utility of D2-40 in pleural fluid cytology in differentiating MM from pulmonary carcinomas. Twenty cases of pleural effusion smears of surgically confirmed MM with their corresponding cell blocks were retrieved from the database of the hospital computer system. We also included 10 cases of metastatic pulmonary adenocarcinoma (PA) and 10 cases metastatic pulmonary squamous cell carcinoma (PSCC) involving the pleural fluid. Cell blocks were formalin-fixed, paraffin embedded, and immunostained for TTF1, p63, calretinin, CK5/6, WT-1, and D2-40. Cases were scored as negative (<5% positivity) or positive (>5% moderate/strong positivity). The positive rates for TTF1, p63, calretinin, CK5/6, WT-1, and D2-40 were as follows: MM (0/20), (0/20), (17/20), (18/20), (19/20), (17/20), for PA (8/10), (0/10), (3/10), (0/10), (0/10), (0/10), and for PSCC (1/10), (10/10), (6/10), (10/10), (0/15), (0/10). The staining pattern for D2-40 was characterized by thick membranous staining. Diffuse cytoplasmic staining by D2-40 was seen in 2 cases of pulmonary carcinoma, counted as negative. Our study showed that in differentiating MM from PA, CK5/6, WT-1, and D2-40 have high specificity and sensitivity for MM. Although calretinin is a sensitive IHC marker for MM, it is not specific since it stained 30% of PA. Conversely, to differentiate between MM and PSCC, p63 and WT-1 are the best available markers. We recommend a panel of CK5/6, p63, D2-40, and WT-1 to differentiate MM from pulmonary carcinomas in effusion cytology specimens.     

Malignant mesotheliomas. Improved differential diagnosis from lung adenocarcinomas using monoclonal antibodies 44-3A6 and 624A12.

Forty-three malignant pleural mesotheliomas and 10 known metastatic pulmonary adenocarcinomas to the pleura were studied by immunohistochemistry using monoclonal antibodies 44-3A6 and 624A12. Monoclonal antibodies 44-3A6 and 624A12 were raised against human pulmonary carcinoma cell lines; they recognize a membrane-associated protein of 40,000 mol wt and a specific sugar sequence of lacto-N-fucopentose III, respectively. Samples were also studied with a broad-spectrum antikeratin antibody and a polyclonal antibody to carcinoembryonic antigen (CEA). These investigations were performed on formalin-fixed and paraffin-embedded tissues. The mesotheliomas comprised only grossly evident, pleurectomized, or pneumonectomized cases; they included 22 epithelial, 15 biphasic, and 6 spindle cell types. Electron-microscopic study was also done on 9 cases. None of the mesotheliomas was immunoreactive to 624A12, while 9/10 metastatic pulmonary adenocarcinomas were convincingly immunoreactive. Monoclonal antibody 44-3A6 immunostained all of the metastatic adenocarcinomas strongly, whereas only 10/43 mesotheliomas were focally and weakly immunoreactive. The latter included 5 epithelial and 4 biophasic mesotheliomas and 1 spindle cell mesotheliomas; the immunoreaction was confined to scattered single cells, and the staining pattern was readily discernible from that of adenocarcinomas. Forty of 43 mesotheliomas were strongly immunoreactive with the broad-spectrum anti-keratin antibody, whereas 8/10 metastatic pulmonary adenocarcinomas showed focal and rather weak staining. Seven of 10 metastatic adenocarcinomas were immunoreactive to anti-CEA antibody, while only 15/43 mesotheliomas displayed weak immunoreactivity. It is concluded that monoclonal antibodies 44-3A6 and 624A12 are excellent phenotypic markers of metastatic pulmonary adenocarcinomas to the pleura and thus are useful for the differential diagnosis of pleural mesotheliomas. Given conventionally fixed and processed tissues, it appears that the combined use of these monoclonal antibodies may be more effective for that differential diagnosis than anti-CEA and anti-keratin antibodies.     

Monoclonal antibody Ber-EP4: Its use in the differential diagnosis of malignant mesothelioma and carcinoma in cell blocks of malignant effusions and FNA specimens

Formal sublimate-fixed cell blocks derived from 129 malignant pleural (and some peritoneal) effusions, 8 benign effusions with reactive mesothelial cells, and 23 FNA specimens, were immunostained with monoclonal antibody Ber-EP4 to assess its ability to distinguish malignant mesothelioma (MM) from carcinoma. Only 2 of 44 (4%) well-characterized MM were Ber-EP4⁺, while none of 8 benign mesothelial proliferations reacted with the antibody. Fifty-seven percent of 23 pulmonary adenocarcinomas (AC) and 60% of 43 pulmonary carcinomas of all other histological types were Ber-EP4⁺. Of 40 metastatic AC originating from breast, gastrointestinal tract, ovary, endometrium, and kidney, 80% were Ber-EP4⁺. The predictive value of positive Ber-EP4 staining in distinguishing AC from MM was 96%. The predictive value of a negative Ber-EP4 in excluding MM was 70%, when the differential diagnosis was adenocarcinoma. These results suggest that Ber-EP4 is helpful in differentiating MM and AC if used together with other discriminating antibodies. © 1994 Wiley-Liss, Inc.     

Is D2-40 a useful marker for distinguishing malignant mesothelioma from pulmonary adenocarcinoma and benign mesothelial proliferations?

Since pulmonary adenocarcinomas, malignant mesotheliomas (MM), and sometimes benign mesothelial proliferations show a great histomorphological resemblance to each other, an immunohistochemical panel is usually necessary for differential diagnosis. D2-40 is an available monoclonal antibody, which is already in use as a lymphatic endothelial marker. It has also been suggested to be useful in identifying the mesothelial differentiation. The aim of this study is to compare D2-40 immunostaining in MM, pulmonary adenocarcinoma, and benign mesothelial proliferations. In this retrospective study, D2-40 immunostaining was investigated in 37 cases of MM, 36 cases of pulmonary adenocarcinoma, and 31 cases of benign mesothelial proliferation. The diagnosis of MM had previously been confirmed by a panel including calretinin, CK5/6, and CEA. Predominantly membranous immunoreactivity was observed in 51% of MMs and in 55% of benign mesothelial proliferations. All the 36 pulmonary adenocarcinomas were negative. These results were statistically significant (p<0.001). We believe that D2-40 may be helpful in the differential diagnosis of MM from pleural involvement of pulmonary adenocarcinoma.     

Malignant mesothelioma: immunohistochemistry and DNA ploidy analysis as methods to differentiate mesothelioma from benign reactive mesothelial cell proliferation and adenocarcinoma in pleural and peritoneal effusions

OBJECTIVE: To determine whether malignant mesotheliomas can be differentiated from adenocarcinomas and benign reactive mesothelial cells in pleural and peritoneal fluids using immunohistochemical analysis in conjunction with DNA ploidy analysis. DESIGN: Sixteen cases of malignant mesothelioma, including epithelial, sarcomatous, and biphasic types, were collected. DNA analysis using flow cytometry and/or image analysis was performed on paraffin-embedded tissue from 15 of the mesothelioma cases, as well as on cytospin cell preparations from samples of pleural and peritoneal fluids from cases with either cytologically proven adenocarcinoma (seven cases) or benign reactive mesothelial cells (seven cases). Immunohistochemical studies were done in 15 mesotheliomas, 5 adenocarcinomas, and 4 benign reactive mesothelial cell effusions. RESULTS: All malignant mesotheliomas tested (100%) stained positively for prekeratin, whereas stains for carcinoembryonic antigen, B72.3, Leu-M1, and Ber-EP4 were negative. Stains vimentin, epithelial membrane antigen, and CA125 were positive in 75%, 75%, and 25% of cases tested, respectively. Benign reactive mesothelial cell cases stained similarly. Adenocarcinomas were more likely to react positively with B72.3, Ber-EP4, and carcinoembryonic antigen, and negatively with vimentin. DNA analysis showed that all benign cases were diploid, while all adenocarcinomas were nondiploid. Fifty-three percent of the malignant mesotheliomas were nondiploid. Sensitivity for detection of nondiploidy was greater for image analysis than for flow cytometry (100% vs 75%). CONCLUSIONS: B72.3, Ber-EP4, carcinoembryonic antigen, and vimentin are useful immunohistochemical markers in differentiating malignant mesotheliomas from adenocarcinomas, whereas immunohistochemistry does not reliably distinguish malignant from benign hyperplastic mesothelial cells. The addition of DNA ploidy studies is useful for differentiating the latter two groups.     

Value of thrombomodulin immunostaining in the diagnosis of mesothelioma

Aims : Even with the benefit of immunohistochemistry and electron microscopy, the differential diagnosis between epithelial mesothelioma and pulmonary adenocarcinoma is often difficult. In most instances, the diagnosis of mesothelioma must be reached by the use of immunohistochemical markers that react with adenocarcinomas, but not with mesotheliomas. The purpose of this study is to determine the value of thrombo-modulin (TM) as a positive marker for mesothelioma when distinguishing epithelial pleural mesothelioma from pulmonary adenocarcinoma. Methods and results : TM was expressed in 28 (80%) of 35 epithelial pleural mesotheliomas, but only five (10.9%) of 46 pulmonary adenocarcinomas had appreciable reactivity for this marker. Conclusion : It is concluded that TM can be useful in separating pulmonary adenocarcinoma from epithelial mesothelioma, but it should be used only in conjunction with other immunohistochemical markers that are currently employed in distinguishing between these two types of malignancies.     

Synchronous diffuse malignant mesothelioma and carcinomas in asbestos-exposed individuals

AIMS: The development of synchronous diffuse malignant mesothelioma and carcinoma in individuals exposed to asbestos is rare. We report nine cases and discuss the medico-legal implications. METHODS AND RESULTS: Five hundred patients seeking compensation for asbestos-related diffuse malignant mesothelioma were reviewed with access to post-mortem data. The study group comprised cases in which a second (non-mesothelial) neoplasm was identified. The study group comprised eight males, one female, mean age 68 years (range 60-75). All individuals gave a history of asbestos exposure. Synchronous malignant mesothelioma with carcinoma was identified in 9/500 (1.8%). Eight malignant mesotheliomas were pleural, one was primary peritoneal in origin. By morphological subtyping there were four epithelioid, three biphasic and two sarcomatoid mesotheliomas. In 6/9 (67%) the second tumour was a primary bronchogenic carcinoma (three adenocarcinomas, two squamous cell carcinomas and one small-cell carcinoma). In 3/9 (33%) the second tumour was a non-bronchogenic carcinoma (colonic, pancreatic and breast ductal adenocarcinoma). No other neoplasms were identified in the cohort of malignant mesotheliomas studied. Five persons had pathological evidence of asbestosis (four had bronchogenic carcinomas, one colorectal adenocarcinoma). Two persons with non-bronchogenic carcinomas had identifiable asbestos bodies but no interstitial fibrosis. In two cases the second neoplasms (primary bronchogenic squamous cell and small-cell carcinomas) were associated with diffuse interstitial fibrosis but no asbestos bodies were seen on light microscopy. In each case transmission electron microscopic mineral analysis revealed an asbestos fibre burden within the background population range for control subjects and well below that seen in cases of established asbestosis. These cases were considered to represent cryptogenic fibrosing alveolitis in subjects with a history of asbestos exposure. CONCLUSIONS: Synchronous malignant mesothelioma with carcinomas in asbestos-exposed workers is rare and identified in 1.8% of 500 malignant mesotheliomas in this series. In most cases the carcinoma represents a primary bronchogenic neoplasm. Primary lung carcinomas are recognized to be asbestos related only when occurring in association with asbestosis. In this series this combination (bronchogenic carcinoma and asbestosis) was seen in four (0.8%) cases. In post-mortem cases for possible malignant mesothelioma it is important to identify any other neoplasia and determine whether it is related to asbestos. Their presence impact upon anticipated life expectancy and in the presence of malignant mesothelioma will affect the compensation settlement.