Mesothelioma Cancer: Introduction to Mesothelioma
The mesothelioma is a tumor that emanates, for example, from cells of the lung, peritoneal or pericardium and encloses the lungs in the form of a coat. It particularly affects people who have had contact with asbestos for a long time. Mesothelioma can be benign or malignant (pleural cancer, breast cancer). Treatment usually consists of surgery combined with chemotherapy.
Learn more about mesothelioma here.
Mesothelioma is an overgrowth (tumor) of the mesothelium. This is a single-layered epithelial tissue that forms the boundary of body cavities such as pleura, pericardium, and peritoneum. It usually lays as a planar tumor around the lungs.
Like most tumors, mesothelioma can appear in benign and malignant forms. The latter is often the result of asbestos exposure. The latency is long: about 35 years elapse between exposure to asbestos and the onset of the first symptoms. If you have been professionally exposed to asbestos and suffer from a malignant mesothelioma, this is considered a recognized occupational disease.
Malignant mesotheliomas are more than 80 percent pleural mesothelioma, ie tumors that emanate from the pleura (pleura: pleura and lung fur). This is referred to as breast cancer or pleural cancer.
In many industrialized countries, asbestos was banned, but the incidence seems to be increasing. Men get three to five times more likely to have mesothelioma than women. The higher the age, the higher the disease risk.
Mesothelioma Diagnosis: examinations and diagnosis
Mesothelioma diagnosis starts with health surveillance and/or a visit to the general practitioner, who examines the work history and, in the event of previous occupational exposure to asbestos, prescribes the necessary investigations, also to keep under control over time any changes. In the case of pleural thickening and/or pleural plaques in workers exposed to asbestos, mesothelioma diagnosis is likely.
The instruments of mesothelioma diagnosis:
• Chest x-ray (to assess pleural thickening and show abnormalities in the mesothelium of the pleura or lungs
• Chest tomography (CT) with contrast medium or spiral CT (to determine the presence, position and possible spread of the tumour to other organs, also in order to define the most suitable type of intervention)
• Tac-pet (to provide additional data on status and extent, identify cancer cells, determine the spread of cancer in lymph nodes or other parts of the body and understand if mesothelial abnormalities are really tumors or other lesions)
• Magnetic resonance imaging (for detailed images of the body’s soft tissues, but without using X-rays. In case of malignant pleural mesothelioma, to assess the health of the diaphragm and any infiltration into the thoracic wall)
• Blood tests (it is not a diagnostic test, but it is useful to confirm the mesothelioma diagnosis obtained with other techniques and to follow the course of the disease during and after treatment. Levels of tumour markers and molecules present in higher doses are measured in case of mesothelial cancer – osteopontine, SMRP, and fibulin-3)
Confirmation of the mesothelioma diagnosis is made only by histological examination and on a biopsy sample, with the collection of the cells with a puncture in the chest (thoracentesis), in the abdomen (paracentesis) or in the cavity around the heart (pericardiocentesis), or with a tac-guided biopsy or even through surgery.
Immunohistochemical analyses confirm with certainty the mesothelioma diagnosis with respect to any other tumours or pathologies, through the analysis of the proteins present on the surface of the cell and the identification of genes typically associated with mesothelial cancer.
In the United States, studies are being conducted to verify the effectiveness of monitoring with measurement of mesothelin, a protein produced by mesothelial cancer cells, which could be a first early indicator for people at high risk.
If you have signs of pleural mesothelioma, you should consult a GP or pulmonologist. To diagnose mesothelioma, the doctor will ask exactly the symptoms and your medical history. Typical questions of the doctor would be for example:
• Since when and how often do you have complaints, such as coughing?
• Are you getting bad air?
• Do you have tough expectoration when coughing?
• Has fever also occurred?
• Do you have contact with the asbestos professionally or privately?
• Do you live or work in the vicinity of astbest processing factories?
• Have you been to areas with natural asbestos deposits?
• Do you live in an old building with asbestos-containing components?
If mesothelioma is suspected, referral to an experienced lung center is useful. To confirm the suspected mesothelioma diagnosis, further physical examinations follow. To record the size of the tumor, imaging techniques such as ultrasound, computed tomography (CT) and magnetic resonance imaging (MRI) can be performed. Final certainty in suspected mesothelioma brings a histological examination of the altered tissue.
Mesothelioma diagnosis imaging procedures
To determine whether water has accumulated between the lung and pleura (pleural effusion), the chest is examined by ultrasound (transthoracic ultrasound). A pleural function (see below) is also performed under ultrasound control.
Computerized tomography (CT) is the best way to detect and detect mesothelioma. In addition, it can be determined by means of CT whether the tumor has already formed secondary tumors (metastases) in the lymph nodes.
If it is suspected that the tumor has spread to the diaphragm or chest wall, magnetic resonance imaging (MRI) can be performed. Also, a so-called positron emission tomography (PET) is useful, especially to detect distant metastases.
In a pleural function, the doctor inserts a fine needle past the ribs into the pleural space and withdraws fluid. In more than half of all patients with pleural cancer, cancer cells can be detected in the pleural effusion. However, a negative result does not rule out pleural mesothelioma.
Mesothelioma Diagnosis of Needle biopsy
In a percutaneous needle biopsy, a needle is advanced into the body from outside to extract a tissue sample from the affected area. The whole is monitored by X-rays, ultrasound, CT or MRI to control the exact position of the needle.
Thoracoscopy (breast mirroring)
To ensure the mesothelioma diagnosis is often a thoracoscopy (breast mirroring) necessary. The pleural cavity is examined endoscopically. In addition, some tumor tissue can be taken during the examination for histologic diagnosis.
The examination of the histological sample should be done by a specialized lung pathologist. The mesothelioma is histologically divided into different forms:
• Epithelial mesothelioma (50 percent of all mesothelioma cases)
• Sarcomatous mesothelioma (25 percent)
• Biphasic mesothelioma (24 percent)
• Undifferentiated mesothelioma (1 percent)
Malignant mesotheliomas show a very varied fine tissue image with various papillary, tubular, adenomatoid, azinous, small cell, spindle cell, lymphohistiocytosis, deziduoid, clear cell, seal ring cell or adenoid cystic differentiations. In the majority of tumors, combinations of different differentiation patterns can be found. The WHO classification of 2004 distinguishes between epithelioid, biphasic, desmoplastic and sarcomatoid subtypes.
Because of this varied fine tissue image – even within the smallest tumor biopsies – a large number of possible differential diagnoses are possible in diagnostics. The differentiation of still benign changes represents a challenge in view of the fact that biopsies may only be a few millimetres in size.
The very heterogeneous differentiation patterns of the malignant mesothelioma and a large number of tumours that can metastasise into the pleura or develop adjacent to it are causative for the difficulties of mesothelioma diagnostics. Macroscopically, pleural carcinoma is indistinguishable from malignant mesothelioma. An increased probability of error (false-positive and false-negative) must be expected.
Immunohistochemical examinations are a standard procedure for the differential diagnostic differentiation of mesothelioma from the metastatic metastasis of another primary tumor.
There is no single specific marker. Different marker panels must be used depending on the tumor subtype and differential diagnostic question. The following markers have proven to be particularly suitable for the mesothelioma diagnosis:
Calretinin (positive marker), MOC31 (negative marker), BerEP4 (negative marker), D2-40 (positive marker), TTF-1 (negative marker), cytokeratin (positive marker) and WT-1 (positive marker).
MOLECULAR PATHOLOGY STUDIES:
Molecular pathological analyses can also help to distinguish malignant mesotheliomas from reactive changes, precursor lesions, pleural carcinoses or sarcomas. Almost all malignant sarcomatoid mesotheliomas of the pleura have a p16 deletion. In malignant epitheliod pleural mesotheliomas, however, the deletion rate is only between 60 and 80 % and in peritoneal mesothelioma, this deletion is even rarer with less than 40 %.
HIGHLY DIFFERENTIATED PAPILLARY MESOTHELIOMAS (WDPM):
Well, differentiated papillary mesothelioma (WDPM) is an exception among mesotheliomas. These usually benign lesions are found by chance during abdominal surgery in other indications, especially in (young) women. Since the WDPM grows only very slowly, usually occurs singularly, is very small and also does not form metastases and is non-invasive, it can be completely removed and the prognosis for the patient is usually very favorable.