Mesothelioma is a very difficult disease for medical professionals to diagnose, because of the fact that it can be easily misdiagnosed as a type of carcinoma, lung cancer, or other type of illness. With further testing, mesothelioma can be classified based on the location of the tumor and also on the type of Mesothelioma cells. These two methods are used in conjunction to assist in identifying the type of mesothlelioma a patient has, along with their cancer stage, location, and cell type.
Clinical presentation and treatment modality can be derived from an analysis of the anatomic location of the tumor. Based on the location, mesothelioma may then be separated into the following types:
Pleural Mesothelioma: Malignant Pleural mesothelioma is a cancer of the cells that make up the pleura or lining around the outside of the lungs and inside of the ribs. It is the most common type of mesothelioma.
Peritoneal Mesothelioma: Malignant peritoneal mesothelioma, sometimes referred to as abdominal mesothelioma, or chrysotile (white asbestos) peritoneal mesothelioma, is a cancer of the cells lining the abdominal cavity, or peritoneum.
Benign Multicystic Peritoneal Mesothelioma: Benign multicystic mesothelioma (BMM) is a rare form of mesothelioma that is not considered cancerous and whose pathogenesis is unclear. Benign multicystic mesothelioma affects the peritoneum of the abdomen. The peritoneum is the protective tissue that surrounds the organs in the abdomen.
Pericardial Mesothelioma: Sometimes doctors refer to this disease as Mesothelioma of the pericardium. Pericardial mesothelioma is the rarest form of mesothelioma, accounting for less than 1% of all cases. Common clinical features are constrictive pericarditis, cardiac tamponade, and cardiac failure.
Malignant Mesothelioma refers to the severity of the tumor in which it has the potential to invade and destroy nearby tissue and/or that may spread (metastasize) to other parts of the body.
Malignant mesotheliomas are then divided into four main histological subtypes based on the type of mesothelioma cells: epithelial, sarcomatous, and mixed or biphasic.
Well-Differentiated Tubulopapillary Type Mesothelioma;
Epithelial Type Mesothelioma (inlcudes tubulopapillary and nonglandular or eptheloid): In general terms the behaviour of epithelial mesotheliomas is similar to that of carcinomas with local spread, large pleural effusions, and metastases to regional lymph nodes;
Sarcomatous Type Mesothelioma (includes desmoplastic mesothelioma): Sarcomatous mesotheliomas are associated more frequntly with distant metastases, little or no effusion, and shorter survival;
Desmoplastic Mesothelioma: Among the biphasic and sarcomatous subtypes is a group of tumours in which more than 50% of the tumour consists of dense, hypocellular collagenous tissue. This is known as desmoplastic mesothelioma;
Biphasic Type Mesothelioma (or “mixed-type”): Mixed mesotheliomas have intermediate features;
Poorly Differentiated Type Mesothelioma (or “undifferentiated”).
Of these types, epitheleal type is the most common; 50% of pleural mesothelioma is of the epitheleal type, and 75% of peritoneal diffuse malignant mesotheliomas are of this type. The next two, biphasic or sarcomatous type, are equally represented types of mesothelioma; 25% in pleural mesothelioma cases and 15% in peritoneal diffuse malignant mesothelioma. The remaining percentage of cases are poorly differentiated or unclassifiable.
Medical professionals will us thoracoscopy and special stains which can be helpful in identifying the particular cellular classification. In some cases, a more thorough examination will be necessary, such as obtaining tissue samples, through a procedure called a biopsy, in which a larger sample may be re-examined.