Advances in Diagnosis of Mesothelioma

Accurate and rapid diagnosis of malignant mesothelioma is important for therapeutic and medicolegal
reasons. The most frequent diagnostic problem is the differentiation of malignant mesothelioma
from adenocarcinoma — a distinction that is particularly difficult to make when the tumor has invaded the pleur
Cytologic Analysis
Cytologic evidence of malignant mesothelioma in the pleural or ascitic fluid is found in 33 to 84 percent
of cases.In some patients, sampling by fineneedle aspiration of the tumor is required to make a diagnosis of malignant mesothelioma, particularly when there is no effusion. A group of immunohistochemical
markers is important in the differential diagnosis of malignant mesothelioma. As the first step, a marker such as calretinin or the Wilms’ tumor 1 antigen (WT1) is used to determine whether the tissue is mesothelial (Fig. 3A and 3B). The second step is to use a marker such as epithelial membrane membrane
antigen (EMA; also known as CA15-3  to determine whether the tissue is malignant. Staining for EMA in a thick peripheral distribution is highly suggestive of malignant mesothelioma Of the two anti-EMA antibodies, E29 has significantly greater specificity than MC-5.
In experienced hands, cytologic analysis is sufficient to make a diagnosis with a high level of confidence in approximately 80 percent of cases of malignant mesothelioma.histopathological analysis Because cytologic findings may be inconclusive or pleural or ascitic fluid may be absent altogether, tumor biopsy is often needed. Closed biopsy (e.g., with the use of an Abrams’ needle) is less likely than direct thoracoscopic biopsy to yield positive results. Immunohistochemical staining to show, for example, expression of epithelial membrane antigen on the luminal aspects of the tumor is essential in the
diagnostic process.Cytokeratin staining helps to confirm invasion and to distinguish malignant
mesothelioma from sarcoma and melanoma. Malignant mesothelioma is distinguished from adenocarcinoma
by the use of specific antibodies. Malignant mesothelioma is characterized by the presence of staining for EMA, calretinin, WT1, cytokeratin 5/6, HBME-1 (an anti–mesothelial cell antibody), or mesothelin (more than 85 percent of epithelioid

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