In this article, we will discuss Malignant Pleural Mesothelioma (Detailed Diagnosis Part-II). So, let’s get started.
Malignant Pleural Mesothelioma (Detailed Diagnosis Part-II)
Histological Diagnosis of Malignant Pleural Mesothelioma
The classic types of malignant pleural mesothelioma are epithelioid, sarcomatous and biphasic, but there are also rare subtypes, such as desmoplastic mesothelioma (that may be confused with benign fibrous pleuritic), small cell mesothelioma and lymphohistiocytoid mesothelioma (that may be confused with lymphoma). Immunohistochemical evaluation is essential for identifying these types. However, no single marker has 100% sensitivity and specificity for mesothelioma, so various monoclonal antibody panels must be determined, of which at least 2 must be positive for mesothelioma. In the epithelioid subtype, these should be preferably calretinin (particularly useful if the nucleus, in addition to the cytoplasma, is stained), Wilms’ tumor antigen 1 (WT-1) or epithelial membrane antigen (EMA) or wide-spectrum, low molecular weight cytokeratins, such as CK5 OR CK6, and 2 negative markers, such as Ber-EP4 (membrane marker) and thyroid transcription factor 1 (TTF-1, nuclear marker). Carcinoembryonic antigen (CEA)
is very useful for distinguishing metastatic carcinoma, particularly of pulmonary origin, from mesothelioma (in which it is practically always negative), and if mesothelioma is suspected in a woman, endoplasmic reticulum(ER) expressionshouldalso be investigated: this never occurs in mesothelioma but is a common feature of metastatic breast tumors. When the tumor contains a sarcomatous component, it often needs to be distinguished from metastases, such as squamous cell lung cancer or transitional cell carcinoma. Although some antibodies used for epithelioid mesothelioma are equally valid for sarcomatous types, some others are often needed for firm evidence, such as p63 and MOC 31.