Malignant epithelioid mesothelioma: anti-mesothelial marker expression correlates with histological pattern

Imaging of Malignant Pleural, Pericardial, and Peritoneal Mesothelioma

Malignant mesothelioma is a rare tumor arising from the mesothelial cells that line the pleura, pericardium, peritoneum, and tunica vaginalis. Imaging plays a primary role in the diagnosis, staging, and management of malignant mesothelioma. Multimodality imaging, including radiography, computed tomography (CT), magnetic resonance imaging (MRI), and F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT), is used in a variety of scenarios, including diagnosis, guidance for tissue sampling, staging, and reassessment of disease after therapy. CT is the primary imaging modality used in staging. MRI has superior contrast resolution compared with CT and can add value in terms of determining surgical resectability in equivocal cases. MRI can further assess the degree of local invasion, particularly into the mediastinum, chest wall, and diaphragm, for malignant pleural and pericardial mesotheliomas. FDG PET/CT plays a role in the diagnosis and staging of malignant pleural mesothelioma (MPM) and has been shown to be more accurate than CT, MRI, and PET alone in the staging of malignant pleural mesothelioma. PET/CT can also be used to target lesions for biopsy and to assess prognosis, treatment response, and tumor recurrence.

Cytoreductive surgery with hyperthermic intraperitoneal chemotherapy for peritoneal mesothelioma: patient selection and special considerations

Malignant peritoneal mesothelioma (MPM) is a rare, aggressive malignancy that typically presents with vague symptoms, ascites, and/or diffuse peritoneal studding. Despite findings of advanced disease within the peritoneal cavity, spread beyond the abdomen is uncommon. Although advances in systemic chemotherapy have been made, cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) remain the mainstay of treatment. Median overall survival of approximately 50 months with CRS/HIPEC has been demonstrated, with age, gender, histologic subtype, peritoneal carcinomatosis index, comorbidities, nodal and extra-abdominal metastases, and completeness of cytoreduction all playing a role in prognosis. In patients with refractory malignant ascites and unresectable disease, complete resolution of ascites and improvement in quality of life have been demonstrated with palliative HIPEC. In appropriately selected patients, CRS/HIPEC plays a critical role in the treatment and palliation of MPM.

Sarcomatoid mesothelioma of tunica vaginalis testis in the right scrotum of a dog

A 12-year-old intact male Welsh Corgi was presented with enlargement of the right scrotum. Both testicles were surgically removed and histopathologically examined. On gross examination, white nodules were found in the epididymis and ductus deferens. Histopathologically, the nodules developed continuously from the tunica vaginalis testis of the right scrotum and consisted of spindle-shaped neoplastic cells that invaded the surrounding tissue. Immunohistochemically, the neoplastic cells were diffusely positive for vimentin, cytokeratin and Wilms tumor-1 (WT-1). Based on these findings, the tumor was diagnosed as sarcomatoid mesothelioma. The dog presented with respiratory distress 122 days after surgery and clinical examination found multiple metastatic lesions in the lung, abdominal lymph nodes and peritoneum. The dog died 144 days after surgery due to disease progression.

Malignant peritoneal mesothelioma: a review

Mesothelioma is a malignancy of serosal membranes. It is most commonly encountered in the visceral pleura with the second most common location in the peritoneum. The diagnosis is very rare and has been linked to toxic exposure to industrial pollutants, especially asbestos. Malignant peritoneal mesothelioma (MPM) commonly presents with diffuse, extensive spread throughout the abdomen with rare metastatic spread beyond the abdominal cavity. Due to its rarity and nonspecific symptoms, it is usually diagnosed late when the disease burden is extensive. Because pleural mesothelioma is more common than MPM, most research has been on the pleural variant and extrapolated for MPM. While treatment advances have been made for MPM, the disease is universally fatal from either abdominal complications secondary to the spread of disease or starvation. Untreated, the life expectancy is less than a year. Cytoreductive surgery (CRS) with heated intraperitoneal chemotherapy (HIPEC) has become the mainstay of therapy with systemic therapies still being developed. We will review the epidemiology of MPM and discuss diagnostic and treatment strategies.

Use of Immunohistochemical Marker Calretinin in the Diagnosis of a Diffuse Malignant Metastatic Mesothelioma in an Equine

Mesotheliomas are rarely reported in animal species. In this report, the occurrence of a diffuse, metastatic mesothelioma in a 6-year-old gray Arabian mare is described. The mare was presented on clinical examination with ascites, bilateral pleural effusion, and pleural roughening. Necropsy revealed abundant fluid in the abdominal and thoracic cavities. The surface of all organs was thick and fibrosed with multiple raised nodules and hemorrhages. Histology was characteristic of a generalized, biphasic mesothelioma with vascular and lymph nodes metastases. It is believed that the primary tumor developed in the pericardium and spread through lymphatics. In this report, calretinin was used as an immunohistochemical marker in the diagnosis of mesothelioma in an equine species for the first time.

Ectopic ACTH secretion (EAS) associated to a well-differentiated peritoneal mesothelioma: case report

BACKGROUND

The association between mesotheliomas and ectopic ACTH secretion has been rarely reported; we present the first case of ectopic ACTH secretion (EAS) associated with a well-differentiated peritoneal mesothelioma in whom the high dose dexamethasone suppression test (HDDST) results and plasmatic ACTH levels were similar to those found in Cushing's disease (CD).

CASE PRESENTATION

A 43-year-old hispanic woman with a 20 year history of treatment resistant diabetes mellitus and arterial hypertension. She had a full moon face, a buffalo hump, increased volume in both supraclavicular regions, purple striae in her arms and abdomen, truncal obesity, polymenorrhea and umbilical hernia. A cortisol suppression test with low dose dexamethasone (LDDST) with a result of 16.6 μg/dL and ACTH plasma levels were measured at 32.6 pg/mL. The high dose dexamethasone test suppression percentage was 84.8% and magnetic resonance imaging (MRI) showed no evidence of pituitary alterations, computed tomography (CT) showed images suggestive of uterine fibroid and an intra-abdominal tumor that correlated with an umbilical hernia, which reinforcement after contrast. Surgery was performed, finding uterine fibroids and paracolic tumor implants as well as on the omentum, bladder, bowel, ovaries and appendix. Pathology reported a well-differentiated peritoneal mesothelioma with positive immunohistochemistry for ACTH.

CONCLUSIONS

Although most cases of ectopic secretion of ACTH derive from rapidly-developing lung tumors, with very high plasma ACTH levels and cortisol suppression percentages with high doses of dexamethasone under 60%, there is a small percentage of slow-developing, chronic tumors that are biochemically undistinguishable from Cushing's disease. Following the expert recommendations regarding imaging techniques it is possible to identify the associated tumor in most cases.

The use of immunohistochemistry in the diagnosis of composite and collision tumors: exemplified by pleural mesothelioma and carcinoid tumor of the lung

A case of a collision lymph node metastasis of a mesothelioma and a carcinoid tumor in a 73-year-old man with a history of asbestos exposure is reported. An interesting finding in this case was that both the mesothelioma and its lymph node metastases exhibited a wide variety of histologic patterns, including one characterized by a solid growth of large cells with abundant, clear, and foamy cytoplasm and another exhibiting deciduoid features. Pathologists should be aware that mesotheliomas can present very unusual morphologic features, such as those seen in the present case, and therefore, should be included in the differential diagnosis of those tumors that can display similar morphology and can metastasize to the serosal membranes. Reexamination of the pneumonectomy specimen in the current case identified a primary peripheral carcinoid tumor. The recognition of a nonasbestos-related tumor in a patient with mesothelioma is important since its presence may have an impact on the patient's life expectancy and, therefore, may affect any compensation settlement.

Immunohistochemistry and Molecular Diagnostics of Pleural Malignant Mesothelioma

Context.—The pathologic approach to pleural-based lesions is stepwise and uses morphologic assessment, correlated with clinical and imaging data supplemented by immunohistochemistry (IHC), and more recently, molecular tests, as an aid for 2 main diagnostic problems: malignant mesothelioma (MM) versus other malignant tumors and malignant versus reactive mesothelial proliferations.

Objective.—To present the current knowledge regarding IHC and molecular tests with respect to MM diagnosis, and in particular, the differentiation of the epithelioid type of MM from carcinoma metastatic to the pleural cavity.

Data Sources.—A review of immunohistochemical features of 286 consecutive MMs from 459 cases of pleural pathology, diagnosed during routine practice from 2003 to 2009. A survey of biomedical journal literature from MedLine/PubMed (US National Library of Medicine) focused on MM and associated tissue-based diagnostic IHC markers and molecular tests.

Conclusions.—The search for a single diagnostic marker of MM has so far been discouraging, given the biologic and phenotypic tumor heterogeneity of MM. The use of antibody panels has gained unanimous acceptance especially in the differential diagnosis between MM and metastatic carcinoma, whereas the usefulness of IHC is more limited when dealing with spindle cell malignancies or distinguishing malignant from reactive mesothelium. A great degree of interlaboratory variability in antibody combinations and clone selection within diagnostic panels still exists. Current investigations aim at selecting the most suitable and cost-effective combination of antibodies by using novel statistical approaches for assessing diagnostic performance beyond the traditional measures of sensitivity and specificity.

"Signet-ring" cells--a caveat in the diagnosis of a diffuse peritoneal mesothelioma occurring in a lady presenting with recurrent ascites: an unusual case report

A diffuse peritoneal mesothelioma is a rare tumor. Exfoliative cytology forms the first step in the diagnosis of mesothelioma, since most of these cases presented with effusion. Despite well established cytomorphological features, a challenge exists in differentiating mesothelial cells, including reactive and malignant types from carcinoma cells and macrophages. Presence of "signet-ring" cells increases the diagnostic challenge as these can be forms of benign and malignant cells. Ancillary techniques like immunohistochemical (IHC) markers and ultrastructural analysis form useful adjunct in substantiating exact diagnosis. We report an unusual case study of a diffuse peritoneal mesothelioma in a 57-years-old lady, with no history of asbestos exposure, presenting with recurrent ascites, diagnosed on ascitic fluid cytology and on histology as an adenocarcinoma, based upon the presence of "signet-ring" cells. On review, clinicopathological correlation with IHC was helpful in forming correct diagnosis.

Primary malignant deciduoid peritoneal mesothelioma: a report of the cytohistological and immunohistochemical appearances

Malignant deciduoid mesothelioma (MDM) is a rare variant of epithelioid mesothelioma. This type of tumor might be associated with the asbestos exposure and carries a poor prognosis in general. MDM was first described by Nascimento et al. in 1994 in a peritoneal lesion of a young woman. And its diagnosis is frequently mistaken with florid mesothelial hyperplasia and peritoneal deciduosis. There are 44 MDM cases reported in the literature up today. A 59-year-old woman patient referred to our clinic was identified with an abdominal mass. Computed tomography of whole abdomen of the patient showed a mass with the widest transverse dimension of 65 × 60 mm at abdominal bifurcation in the mesenteric region. The patient was diagnosed with MDM after the cytopathological examination of the fine needle aspiration biopsy performed from the mass. Consequently, she received a total mass excision and right hemicolectomy under general anesthesia. The cytomorphological appearance of the ascitic fluid is detailed for the first time by Gillespie et al. and is described only in two manuscripts. In the present study, we aimed to report a case of a 59-year-old woman since she was diagnosed with MDM and because her cytological findings were further supported by histomorphological and immunohistochemical evaluations of the operation material obtained from the patient.

Benign and Malignant Mesothelial Proliferation

Malignant mesothelioma (MM) is a rare primary malignant tumor of the surface serosal cells. The diagnosis of MM is challenging with a broad differential diagnosis. For many decades, studies have focused on distinguishing MM from other types of cancer; however, benign mesothelial cell hyperplasia, especially in small biopsies, has emerged as a major problem. The features of pleural lesions are somewhat different from peritoneal diseases, and this article primarily focuses on pleural diseases. Thorough interpretation and correlation of clinical, radiologic, and pathologic findings are essential for a correct diagnosis.

Apparent Alveolar Bronchiolar Tumors Arising in the Mediastinum of F344 Rats

Rare tumors were observed in chronic studies in F-344 rats that were purely or largely free in the mediastinal cavity, yet had the histological architecture of alveolar bronchiolar tumors. They had originally been diagnosed as either pulmonary alveolar bronchiolar tumors, mediastinal mesotheliomas, or thymomas. The authors described these tumors, estimated the fraction of thoracic tumors that they represented, and carried out a preliminary immunohistochemical investigation of whether they were of pulmonary or mesothelial origin. Sections of 715 thoracic tumors originally diagnosed as alveolar bronchiolar tumors, mesotheliomas, or thymomas from control or treated F-344 rats in NTP two-year studies were reviewed. Thirty (4%) were found to be purely or largely mediastinal, yet to have an alveolar bronchiolar histological pattern. A subset of these tumors and some typical intrapulmonary alveolar bronchiolar carcinomas and pleural mesotheliomas were immunostained for Clara cell secretory protein (CCSP), β-tubulin IV, and Wilm’s tumor 1 susceptibility gene products (WT1). The tumors with the histological architecture of alveolar bronchiolar tumors immunostained positive for CCSP and negative for WT1, implying they might have been of alveolar bronchiolar origin, despite their predominantly mediastinal location, although more certain identification would require the use of a larger panel of antibodies.

Problems in mesothelioma diagnosis

Many centres are now seeing increasing numbers of patients with malignant mesothelioma. This presents pathologists involved in making the diagnosis with a number of problems, which can be divided into those encountered in making the distinction between mesothelioma and benign changes and those experienced in separating mesotheliomas from other types of epithelial and connective tissue tumours. Immunohistochemistry plays a major role in helping to make the diagnosis, but it should be interpreted with due regard to the clinical setting and radiological features, and with a knowledge of the wide morphological variations seen in mesothelioma. This review identifies some of these problems and addresses the uses and limitations of immunohistochemistry in different situations. It includes a discussion of some of the less common variants of mesothelioma and other pleural-based tumours that enter into the differential diagnosis.

Multilocular cystadenoma and cystadenocarcinoma of the prostate

BACKGROUND

Multicystic prostatic tumors are rare, with only a few reported cases of prostatic cystadenoma and cystadenocarcinoma in the scientific literature.

METHODS

A retrospective review of our tumor registry over the last 25 years identified 2 rare cystic tumors of the prostate: 1 multilocular cystadenoma and 1 multilocular cystadenocarcinoma.

RESULTS

The first case illustrates the clinical and pathologic features of prostatic multilocular cystadenoma. A 42-year-old man presented with a 16-cm suprapubic mass causing displacement of adjacent visceral organs. Pathologic examination after prostatectomy confirmed it to be a multilocular cystadenoma of the prostate. The patient's postoperative course was uneventful, and his serum prostate-specific antigen level remained at < or =0.04 ng/ml throughout the course of his disease. In the second case, we present an 80-year-old male presenting with a 12-cm cystic mass of the prostate. His serum prostate-specific antigen level remained at > or =9.0 ng/ml throughout the course of his disease. The tumor had an aggressive local growth pattern, with invasion into perirectal adipose tissue. This patient underwent a pelvic exenteration, followed by adjuvant systemic chemotherapy and complete androgen blockade. Despite aggressive treatment, he had 3 recurrences over 4 months but remains alive with disease at 23-month follow-up.

CONCLUSIONS

Cystadenocarcinoma of the prostate is locally aggressive and should be included in the differential diagnosis of cystic lesions of the prostate.

Ten cases of feline mesothelioma: an immunohistochemical and ultrastructural study

In the cat only 10 cases of mesothelioma, mainly of the peritoneum, have been previously reported. This paper describes a further 10 cases, eight pleural and two peritoneal, in males and females aged 1-17 years. Histologically, five tumours were epithelial, three fibrosarcomatous and two biphasic. Immunohistochemical markers used in human pathology for the identification of mesotheliomas include vimentin, cytokeratin (CK) AE1/AE3, HBME-1, CK 5/6, calretinin, thrombomodulin, carcinoembryonic antigen (CEA), CD15, E-cadherin and desmin. All 10 feline mesotheliomas were positive for vimentin and CK AE1/AE3, six were positive for HBME-1, two for CK5/6, three for CEA and four for E-cadherin. All were negative for desmin and calretinin. Antibodies to thrombomodulin and CD15 failed to cross-react with feline tissues. Electron microscopy, performed in four cases, revealed microvillar structures, desmosomes and intracytoplasmic lumina, confirming its value as a diagnostic tool. The study showed that mesothelial marker antibodies commonly used in human patients can be used for the diagnosis of feline mesothelioma, preferably as a panel of antibodies rather than only one.

The immunohistochemical profile of malignant mesotheliomas of the tunica vaginalis: a study of 20 cases

Malignant mesotheliomas of the testis arise from the tunica vaginalis, formed from the evagination of the abdominal peritoneum into the scrotum. The immunohistochemical profile of the tunica vaginalis and associated neoplasms is often extrapolated from thoracic studies. Testicular series are uncommon, usually derived from previous case studies and literature reviews. The immunohistochemical findings in 20 cases originally diagnosed as malignant mesotheliomas are presented. Archival testicular malignant mesothelioma specimens from 1959 to 2004 were collected from hospitals throughout the United Kingdom and from the authors' own archives. Hematoxylin and eosin-stained sections were reviewed, and selected sections from each case were then examined using an immunohistochemical panel of eight antibodies: calretinin (Zymed, 1:200), epithelial membrane antigen (EMA) (DAKO, 1:50), thrombomodulin (DAKO 1:5), CK7 (DAKO, 1:100), CK5-CK6 (DAKO, 1:10), BerEp4 (DAKO, 1:25), carcinoembryonic antigen (CEA) (DAKO, 1:10), and CK20 (DAKO, 1:100). The EnVision technique was used for all antibodies. Sections were reviewed independently by three pathologists. Electron microscopy was performed on selected cases. In all cases, the morphologic light microscopy criteria for a diagnosis of malignant mesothelioma were present. However, two tumors were later excluded from the study because of diffuse strong positive immunostaining with CK20 and BerEp4 and an ultrastructural appearance of adenocarcinoma. Of the remaining cases, 15 of 18 (83%) were purely epithelioid in type, showing a mixture of papillary, tubular, and solid patterns, and 3 of 18 (17%) showed a mixed sarcomatoid/epithelioid pattern. All cases were positive for calretinin and EMA (100%), 16 of 18 (89%) were positive for thrombomodulin, and 15 of 18 (83%) were positive for CK7. CK5-CK6 positivity was present in 13 of 18 (72%) but varied in strength and distribution; 2 of 18 (11%) were positive for BerEp4. All the cases were negative for CK20 and CEA. Four of the 18 cases were examined by electron microscopy, which revealed long thin microvilli supporting a diagnosis of malignant mesothelioma. This study has shown that the immunocytochemical profile of testicular malignant mesotheliomas is similar to those arising in the pleura, with diffuse positivity for calretinin, EMA, thrombomodulin, and CK7, and negative for CK20 and CEA. Focal weak positivity may be encountered with BerEp4. However, histopathologists should be aware of the variability in CK5-6 staining in testicular specimens when compared with pleural mesotheliomas.

Lymphohistiocytoid mesothelioma: a clinical, immunohistochemical and ultrastructural study of four cases and literature review

Lymphohistiocytoid mesothelioma (LHM) is a term proposed to designate a variant of mesothelioma that assumes a histiocytoid morphology and contains intense lymphocytic infiltrates. Reports on this variant are few, and its clinicopathologic and ultrastructural characteristics are still to be defined. The authors have studied 4 such cases that were identified among 120 mesotheliomas in the electron microscopy (EM) files of a single institution between 1982 and 2002. Histologically, all 4 lesions were composed of diffuse proliferations of cells with a histiocytoid appearance, admixed with an intense lymphocytic infiltrate. All 4 were associated with an unequivocal sarcomatoid component. Immunohistochemical (IHC) studies showed that the majority of histiocytoid cells were positive for CD68 and vimentin in all 4 cases, suggesting fibrohistiocytic differentiation. Immunoreactivity for calretinin and AE1:AE3 was only very focally identified in 3 of 4 cases. All cases were negative for CEA (M), Leu-M1, and B72.3. The lymphocytic component in all 4 cases was almost entirely composed of CD3- and CD8-positive, small, mature T cells, with only a minor component of CD20-positive cells and occasional eosinophils. Although all cases contained numerous CD68 positive atypical cells, co-expression of CD68 and either calretinin or keratin by individual cells was difficult to demonstrate by immunohistochemistry. Ultrastructurally, 3 of the 4 cases demonstrated very focal mesothelial differentiation as evidenced by long and slender surface microvilli, including the case with negative immunoreactivity for calretinin and cytokeratin. Review of the literature yielded 6 additional LHM cases. Analysis of all 10 cases showed a male predominance (8:2) with a mean age of 58 years (31-73 years). All 10 cases involved the pleura. Three of 10 patients had known asbestos exposure. Six of 10 patients died of disease at 2-20 months after the diagnosis (mean, 6.9 months). The findings suggest that LHM is a distinct morphological variant of sarcomatoid mesothelioma for which mesothelial differentiation is difficult to document. Many of the cells composing these tumors exhibit fibrohistiocytic differentiation. The unusual morphological pattern of LHM makes a combined modality approach, including IHC, EM, and a knowledge of the clinical/radiologic findings, essential in achieving a correct diagnosis.

Pathology of mesothelioma

In this article, progress in distinguishing mesothelioma from mesothelial hyperplasia and fibrosing pleuritis was discussed. Advances in the immunohistochemical characterization of mesothelioma, in the recognition of entities that mimic mesothelioma, and in their distinction from mesothelioma were reviewed. Cytogenetic and molecular genetic contributions to the diagnosis of pleural synovial sarcoma were briefly summarized. The diagnosis of epithelial type mesothelioma can be established in most cases. Several mesotheliomas, however, especially rare subtypes, and sarcomatoid, desmoplastic, and poorly differentiated mesotheliomas continue to present diagnostic challenges.

Establishment of permanent cell lines purified from human mesothelioma: morphological aspects, new marker expression and karyotypic analysis

This study reports the establishment of three major subtypes of human mesothelioma cells in tissue culture, i.e. the epithelioid, sarcomatoid and biphasic forms, and compares their phenotypic and biological characteristics. Primary cells isolated from biopsies or pleural exudates were subcultured for over 50 passages. We evaluated immunoreactivity using various mesothelial markers related to histological patterns of these cell lines. For epithelioid cells, calretinin and cytokeratin were found to be useful and easily interpretable markers as for control mesothelial cells. The biphasic form was only partially positive and the sarcomatoid type negative. Vimentin was expressed by all cell lines. BerEP4, a specific marker for adenocarcinoma, was negative. Interestingly, while the macrophage marker CD14 was negative, immunoreactivity for a mature macrophage marker (CD68) was expressed by all cell types, suggesting that this marker might constitute an additional tool useful in the differential diagnosis of mesothelioma. At the ultrastructural level, a cell surface rich in microvilli confirmed their mesothelial origin. PCR analysis revealed that none of the cell lines contained SV40 DNA. Karyotypic analyses showed more complex abnormalities in the epithelioid subtype than in the sarcomatoid form. These cell lines may be useful in the study of cellular, molecular and genetic aspects of the disease.

The immunohistochemical diagnosis of mesothelioma: a comparative study of epithelioid mesothelioma and lung adenocarcinoma

A large number of immunohistochemical markers that can facilitate the distinction between epithelioid pleural mesotheliomas and pulmonary peripheral adenocarcinomas have recently become available. The aim of this study is to compare the value of these new markers with others that are already commonly used for this purpose and to determine which are, at present, the best for discriminating between these malignancies. Sixty epithelioid mesotheliomas and 50 lung adenocarcinomas were investigated for expression of the following markers: calretinin, cytokeratin 5/6, WT1, thrombomodulin, mesothelin, CD44S, HBME-1, N-cadherin, E-cadherin, MOC-31, thyroid transcription factor-1 (TTF-1), BG-8 (Lewisy), carcinoembryonic antigen (CEA), Ber-EP4, B72.3 (TAG-72), leu-M1 (CD15), CA19-9, epithelial membrane antigen (EMA), and vimentin. All (100%) of the mesotheliomas reacted for calretinin, cytokeratin 5/6, and mesothelin, 93% for WT1, 93% for EMA, 85% for HBME-1, 77% for thrombomodulin; 73% for CD44S, 73% for N-cadherin, 55% for vimentin, 40% for E-cadherin, 18% for Ber-EP4, 8% for MOC-31, 7% for BG-8, and none for CEA, B72.3, leu-M1, TTF-1, or CA19-9. Of the adenocarcinomas, 100% were positive for MOC-31, Ber-EP4, and EMA, 96% for BG-8, 88% for CEA, 88% for E-cadherin, 84% for B72.3, 74% for TTF-1, 72% for leu-M1, 68% for HBME-1, 48% for CD44S, 48% for CA19-9, 38% for mesothelin, 38% for vimentin, 30% for N-cadherin, 14% for thrombomodulin, 8% for calretinin, 2% for cytokeratin 5/6, and none for WT1. After analyzing the results, it is concluded that calretinin, cytokeratin 5/6, and WT1 are the best positive markers for differentiating epithelioid malignant mesothelioma from pulmonary adenocarcinoma. The best discriminators among the antibodies considered to be negative markers for mesothelioma are CEA, MOC-31, Ber-EP4, BG-8, and B72.3. A panel of four markers (two positive and two negative) selected based upon availability and which ones yield good staining results in a given laboratory is recommended. Because of their specificity and sensitivity for mesotheliomas, the best combination appears to be calretinin and cytokeratin 5/6 (or WT1) for the positive markers and CEA and MOC-31 (or B72.3, Ber-EP4, or BG-8) for the negative markers. An extensive and detailed review of the literature is also provided.

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.