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.     

Pulmonary epithelioid hemangioendothelioma mimicking mesothelioma

An intrathoracic mass was discovered on magnetic resonance imaging (MRI) of the spine in a 37-year-old Caucasian man with a 1 year history of progressively severe upper back pain. A subsequent chest CT scan indicated a 4 cm left hilar mass, extending to the apex and encasing a portion of the left bronchus and pulmonary artery. Initial bronchoscopic and transthoracic biopsies failed to obtain diagnostic material. The patient underwent thoracotomy and was found to have a locally advanced, surgically unresectable lung tumor, involving the pleura, pericardium and diaphragm. The patient failed to respond to radiochemotherapy, and died 11 months following the diagnosis with tamponade and metastasis to the skin of the thoracoabdominal wall. Histologically the tumor had an epithelioid and spindled appearance, without high-grade histological features, and was initially thought to represent biphasic diffuse malignant mesothelioma. Positive immunohistochemistry for vascular markers (CD31, CD34, and FLI-1) disclosed the vascular nature of the tumor. Mesothelioma markers were universally negative and cytokeratin was focally reactive only in some epithelioid cells. Epithelioid hemangioendothelioma is a rare tumor in the lung that can mimic other more common pathological entities, and should be included in the differential diagnosis of unusual pulmonary neoplasms with epithelioid or biphasic morphology.     

Immunohistochemical marker panels for distinguishing between epithelioid mesothelioma and lung adenocarcinoma

The distinction between epithelioid mesothelioma and lung adenocarcinoma remains an important diagnostic challenge for surgical pathologists. The aim of the present study was to select a limited and appropriate panel of antibodies that can differentiate between epithelioid mesothelioma and lung adenocarcinoma. Specimens of 90 epithelioid mesotheliomas and 51 lung adenocarcinomas obtained from Japanese cases were examined using calretinin, WT1, AE1/AE3, CAM5.2, cytokeratin (CK) 5/6, vimentin, epithelial membrane antigen (EMA), thrombomodulin, CEA, CA19-9, and CA125. Ninety-six percent of epithelioid mesotheliomas were positive for calretinin; 99% for WT1; 100% for AE1/AE; 97% for CAM5.2; 70% for CK 5/6; 91% for vimentin; 96% for EMA; 71% for thrombomodulin; 77% for mesothelin; 7% for CEA; 17% for CA19-9; and 85% for CA125. In contrast, 33% of lung adenocarcinomas were positive for calretinin; 16% for WT1; 100% for AE1/AE3, CAM5.2, and EMA; 41% for CK 5/6; 47% for vimentin; 20% for thrombomodulin; 69% for mesothelin; 98% for CEA; 73% for CA19-9; and 80% for CA125. For distinguishing between epithelioid mesothelioma and lung adenocarcinoma, the combination of CEA, calretinin and each WT1 or thrombomodulin was suggested to be the best panel of immunohistochemical markers.     

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.     

Malignant mesothelioma with intracytoplasmic crystalline inclusions

A 60-year-old female presented with a history of hoarseness, cough, chest pain, and dyspnea and a needle biopsy sample was submitted for histology. Light microscopy showed sheets of tumor cells with eosinophilic cytoplasm containing multiple crystals and eccentrically located nuclei. Electron microscopy showed large intracytoplasmic crystalloid inclusions. No crystalloid structures were found extracellularly. The tumor cells also had long slender microvilli and cell junctions, the features being consistent with a malignant epithelial mesothelioma. In the authors' experience this is a rare finding. The clinical information initially received was poor and electron microscopy was essential in making the correct diagnosis.     

Caveolin-1 is a novel immunohistochemical marker to differentiate epithelioid mesothelioma from lung adenocarcinoma

Aims:  The incidence of mesothelioma is increasing in Europe, Japan and other developing countries. There is difficulty in the accurate diagnosis of mesothelioma and its differentiation from lung adenocarcinoma. Mesothelioma shows a complex immunohistochemical profile. Therefore, the use of a immunohistochemical panel that includes both positive and negative mesothelial markers has become a general rule for its accurate diagnosis. However, they are still not sufficient. The aim was to assess the diagnostic utility of caveolin-1 (Cav-1), which is expressed in endothelial cells, alveolar type I pneumocytes and mesothelial cells, as a novel positive marker of mesothelioma.
Methods and results:  An immunohistochemical study of 80 cases of epithelioid mesothelioma and 80 cases of lung adenocarcinoma was performed for the analysis of the expression of Cav-1 and other markers. Cav-1 expression with a membranous and/or cytoplasmic pattern was found in all of the epithelioid mesothelioma. Of these, 42 cases (52.5%) showed Cav-1 expression in >50% of tumour cells, 34 cases (42.5%) in 6–50% of tumour cells, and four cases (5.0%) in <5% of tumour cells. In contrast, only six cases (7.5%) of lung adenocarcinoma showed focal Cav-1 expression in the cytoplasm of the tumour cells. The sensitivity and specificity of Cav-1 expression for the differentiation of epithelioid mesothelioma from lung adenocarcinoma were 100 and 92.5%, respectively. This is comparable or even superior to that of currently available positive markers such as calretinin or D2-40.
Conclusions:  Cav-1 is a novel immunohistochemical marker for the differentiation of epithelioid mesothelioma from lung adenocarcinoma.     

Malignant deciduoid mesothelioma of the pleura: report of two cases with long survival

AIMS: To present two rare cases of malignant mesotheliomas with deciduoid features arising in the pleura, both with long survival. METHODS AND RESULTS: These two cases of deciduoid mesotheliomas were observed in adult patients (one 73-year-old male and one 23-year-old female). Only the male had a history of occupational asbestos exposure, whereas the woman had a history of familial mesothelioma. A deciduoid morphology was predominant and focal areas with tubular-papillary features were noted. The tumour cells were positive for cytokeratins, HMBE-1, calretinin, EMA and mitochondrion antibodies. The follow-up data did not suggest a particularly poor prognosis; the mean survival observed was 23 months (17 and 39 months, respectively). CONCLUSIONS: This deciduoid mesothelioma histological subtype does not appear to represent an unfavourable prognostic category.     

Malignant mesothelioma of the pericardium: case reports and immunohistochemical studies including Ki-67 expression

Pericardial malignant mesothelioma (PMM) is extremely rare compared with pleural cases of mesothelioma. We present the clinical and pathological features of three autopsy cases with PMM. All three cases showed rapid progress and died of heart failure. Detailed examination was obtained from the autopsy. Macroscopic appearances of each case showed a thickened pericardium due to tumor invasion. Microscopic observations of all cases led to a diagnosis of epithelial-type malignant mesothelioma (MM). The results of immunohistochemical examinations were similar to the previous published work on pleural mesothelioma. To disclose the pathological characteristics of PMM, we analyzed Ki-67 labeling index (LI) of three cases of PMM and five cases of pleural MM that died within 2 years. The difference of Ki-67 LI between PMM and pleural MM was not significant (P > 0.05). The poor prognosis of patients with PMM must be caused by restricted cardiac wall motion due to tumor involvement, in addition to the tumor proliferation itself.     

Malignant mesothelioma with a pronounced myxoid stroma: a clinical and pathological evaluation of 19 cases

Mesothelioma with a pronounced myxoid stroma has been identified as a morphological pattern that might portend a better prognosis. Reports on this type of cases are few. Its clinical and pathological features are not defined. In this study, we identified 19 such cases from a series of 234 pleural mesotheliomas and performed a comprehensive clinical and pathological analysis. The inclusion criteria were mesotheliomas with at least 50% of the tumor exhibiting a pronounced myxoid stroma that occupied more than 50% of the tumor volume (designated as myxoid mesothelioma). There were ten males and nine females, with a median age of 58 years. Forty seven percent of the patients had probable or definite asbestos exposure. Patients presented at various stages [International Mesothelioma Interest Group (IMIG) stage II, 4; stage III, 9; and stage IV, 6]. Most (16/19) patients were treated by extrapleural pneumonectomy with adjuvant radiation or chemotherapy or both. Overall, the median survival rate was 36 months (median follow-up time, 17 months), and the 2-year survival rate was 79%. Histologically, the tumor cell component was entirely epithelioid without significant cytologic atypia. The myxoid material stained positive for Alcian blue, and the staining diminished after treatment with hyaluronidase in 12 of 12 cases. The tumor cells showed a typical mesothelial immunophenotype. Ultrastructurally, all six tumors examined had typical mesothelial-type surface microvilli and a moderately electron-dense extracellular amorphous material that often formed a haze enmeshing the surface microvilli. Hyaluronic acid-type, fern-like crystals were noted in all cases. These findings show that myxoid mesotheliomas represent a group of epithelioid mesotheliomas that have retained the secretory activity of normal mesothelium. Patients may present at different stages, but survival appears to be superior to that of epithelioid mesotheliomas in general. Our study emphasizes the need for better attention to histologic subtypes, particularly in the context of prognostically or therapeutically oriented investigations of this lethal disease. Presented in part at the 93rd annual meeting of the United States and Canadian Academy of Pathology, Vancouver, British Columbia, Canada, 6–12 March, 2004     

Malignant peritoneal mesothelioma: Quantitative analysis of asbestos burden

Malignant mesotheliomas develop commonly in the pleural cavity and rarely arise in the peritoneal cavity. It is well established that asbestos exposure is related to malignant pleural mesothelioma, but the asbestos burden in the abdominal cavity in patients with malignant peritoneal mesothelioma has not been well studied. The purpose of the present study was therefore to report on an autopsy case of malignant peritoneal mesothelioma with quantitative analysis of the asbestos burden in tissues from the pleura and organs in the abdominal cavity. The patient was a 67-year-old man with a history of asbestos exposure. The peritoneum was thickened with diffuse tumor proliferation. This patient was diagnosed as having malignant peritoneal epithelioid mesothelioma. The number of asbestos fibers was >10 000/g dry tissue in all samples examined except in the small intestine. The number of asbestos fibers in the stomach was 53 000/g, which was higher than that in a control asbestosis subject. The existence of numerous asbestos fibers found in the abdominal cavity suggests that asbestos stimuli are related to the tumorigenesis of malignant peritoneal mesothelioma.     

Malignant mesothelioma of the pleura

Summary Between March 1981 and February 1985, 93 out of 132 patients with a histologically confirmed diagnosis of malignant pleural mesothelioma were eligible for therapy and were prospectively assigned to receive either combined therapy or best supportive care, according to their personal preferences. Fifty-seven patients underwent multimodal therapy including surgical resection where possible, polychemotherapy, and radiation therapy in case of partial remission. Thirty-six patients received maximal supportive care only, as did 39 patients who were not eligible for treatment. The median survival was 13 months for treated patients compared to 7 for those receiving best supportive care and 5 for patients not amenable to treatment. Median progress-free survival was 6, 2, and 1 month respectively. Surgical resection did not prolong life expectancy within the treated group. In view of significant differences in the distribution of various cofactors over the two study groups, stepwise Cox model analyses were performed. Prognostic nontreatment variables related to prolonged survival were: good performance status, stage I and II, absence of chest pain, age below 50 years, and epithelial histology. Although in the Cox model analyses the survival improvement of patients being treated could be greatly attributed to other cofactors, multimodal treatment showed some prolongation of life expectancy.     

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.     

Benign papillary mesothelioma of peritoneum: a histological, histochemical and ultrastructural study of six cases

Six cases of localized benign papillary mesothelioma of peritoneum were retrieved from laboratory files over a 20-year period. One presented because of pain following torsion and the remaining five were incidental findings at operation. Light microscopy showed a delicate papillary stroma covered by a single layer of mesothelial cells. The mesothelial cells often showed punctate periodic acid-Schiff staining of cytoplasm. The brush border and stroma showed alcian blue positive staining which was abrogated by prior incubation with hyaluronidase. Electron microscopy revealed typical features of mesothelial cells with long microvilli, rough endoplasmic reticulum in relation to mitochondria, bundles of microfilaments, and tight junctions. Between cells there was a series of intercommunicating channels containing occasional lymphocytes and debris. These features are compared with nodular mesothelial hyperplasia, malignant mesothelioma and adenomatoid tumours of the genital tract. The necessity to distinguish benign papillary mesothelioma from metastatic carcinoma is stressed and relies on the recognition of their mesothelial origin.     

Adenomatoid mesothelioma with intranuclear inclusion bodies: A case report with cytological and histological findings

We report a very unusual cytologic feature, intranuclear inclusion bodies, in mesothelioma of a predominantly adenomatoid type. The patient, a 57‐year‐old woman, was presented with dyspnea and right pleural effusion. Pleural aspiration cytology revealed many cohesive ball‐like clusters, with a tubular pattern, composed of small atypical cells displaying a high‐nuclear‐cytoplasmic ratio. They had a nuclear groove and irregular intranuclear inclusion bodies. Right lung partial resection with thoracoscopy revealed that a white tumor had proliferated along the pleural surface at S⁸. Histology revealed nodular tumor cells forming dilated structures mixed with small tubular or glandular structures similar to those seen in benign adenomatoid tumors. These tumor cells had invaded peripheral lung tissues. Such inclusion bodies have not been reported earlier in mesothelioma. On the basis of this observation, we propose that the adenomatoid type of malignant mesothelioma be added to the differential diagnosis of malignant effusions when tumor cells with nuclear grooves and intranuclear inclusions are found in pleural aspiration cytology. Diagn. Cytopathol. 2014;42:436‐440. © 2012 Wiley Periodicals, Inc.     

Podoplanin as a marker for mesothelioma

Podoplanin is a specific marker for lymph vessel endothelial cells. It was noted that podoplanin is expressed in reactive mesothelial cells. The utility of podoplanin for the histological diagnosis of tumors was then investigated, especially for mesothelioma. Immunohistochemical study of podoplanin was carried out in five malignant mesotheliomas and 118 other tumors including 93 adenocarcinomas, four squamous cell carcinomas, six gastrointestinal stromal tumors and five endocrine tumors. Immunoreactivity for podoplanin was demonstrated on the cell membrane of tumor cells for all mesotheliomas. All other tumors were negative for podoplanin. Among the many antibodies used for differential diagnosis of malignant mesothelioma, podoplanin has the potential to be an excellent tumor marker in both specificity and sensitivity. The utility of podoplanin as a marker for mesothelioma will be confirmed by further studies.