Mesothelioma Pathology - Making the Diagnosis of Mesothelioma

Mesothelioma Pathology
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Usefulness of immunohistochemistry in an accurate diagnosis.

The histochemical staining of hyarulonic acid and electron microscopic studies have been widely used in the past for making a differential diagnosis between mesothelioma and other tumors. However, immunohistochemical stains are currently the method of choice because of the simplicity and ease of these techniques. Many antibodies have been detected for use in immunohistochemical staining techniques aimed at diagnosing mesothelioma, but as yet there is no antibody that is completely specific for mesothelioma and on which a pathological diagnosis of mesothelioma can be singly based. Therefore, the combination of a number of antibodies as positive or negative markers is important, and an assessment of the results in a comprehensive manner is necessary.

In the case of epithelioid mesothelioma, calretinin, WT1, thrombomodulin, mesothelin and D2-40 can be applied as a mesothelial cell marker. CEA, TTF-1, Napsin A and surfactant apoprotein are used as markers for lung adenocarcinoma. In the case of ovarian serous papillary adenocarcinoma, we recommend CEA, Ber-EP4, MOC-31 and ER (estrogen receptor) as positive markers.

The antibodies chosen for sarcomatoid mesothelioma are very different from those used for epithelioid mesothelioma. In the case of sarcomatoid mesothelioma, cytokeratin (AE1/AE3 or CAM5.2 as antibodies) exhibits a high specificity and is the most useful. On the other hand, because the diagnosis for true sarcoma is based on the specific differentiation of tumor cells, mesothelioma is eliminated by making its differentiation clear. For example, the following antibodies are known to be useful: MyoD1, desmin and myoglobin for rhabdomyosarcoma; desmin, α-SMA and h-caldesmon for leiomyosarcoma; S-100p for malignant nerve sheath tumor; KP-1 for malignant fibrous histiocytoma.

The most difficult tumor to be differentiated from sarcomatoid mesothelioma of pleura is sarcomatoid carcinoma (spindle cell carcinoma, pleomorphic carcinoma) of the lung. When immunohistochemical stainings are used, both respond positively to cytokeratin. In this case, therefore, the gross finding or the clinical diagnosis by imaging is very important, as already mentioned.

Immunohistochemical stains may be useful in differentiating between fibrous pleuritis and desmoplastic mesothelioma. Desmin is positive for spindle cells of the fibrous pleuritis, while desmin is negative for tumor cells of the sarcomatoid mesothelioma. The combination of EMA, desmin and p53 is useful for differentiating between reactive mesothelial hyperplasia and early-stage epithelioid mesothelioma. Reactive mesothelial cells are positive for desmin and negative for EMA and p53.

Compensation or relief of patients.

In the compensation system for occupational exposures to asbestos and in the new law for non-occupational exposure to asbestos, if the diagnosis of mesothelioma is certain, it can almost always be presumed to be related to asbestos exposure and the patients can receive compensation or relief. Therefore, the accuracy of the pathological diagnosis as mesothelioma is very important. However, a rough estimate is that approximately 10–15% of mesothelioma patients receive an inadequate diagnosis. In the committee for the judgement of patients’ relief, 30% of applicants are judged as not having mesothelioma or the decision is deferred until additional evidence is provided. It is therefore essential that Japanese clinicians and pathologists make an effort to improve the accuracy of the diagnosis as mesothelioma. In particular, the pathologists must improve the accuracy of the pathological diagnosis using adequate immunohistochemical stains.

Mesothelioma Pathology - Making the Diagnosis of Mesothelioma
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🔗 https://www.ncbi.nlm.nih.gov/p....mc/articles/PMC26982

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