A mesothelioma diagnosis may often be classified as another condition because the symptoms are similar to those of other illnesses. Even today, a mesothelioma diagnosis can be classified as lung cancer, which is an entirely different disease. Mesothelioma is a cancer of the lining of the chest, lung, and abdominal cavity and has been linked to high levels of workplace and non-occupational exposure to asbestos. (See Mesothelioma Prognosis). Once the physician establishes the appearance of abnormalities on the mesothelium membrane, then several questions develop regarding the type of illness that is appearing on imaging studies, whether or not the perceived growths are benign, and whether or not they are in fact mesothelioma or some other form of carcinoma associated with epithelial cells.
A mesothelioma diagnosis commonly begins with a complete medical history review and physical examination of a patient who suffers from mesothelioma symptoms and signs including shortness of breath, chest pains, swollen abdomen, a dry, persistent cough – or in the case of pericardial mesothelioma, erratic behavior in the cardiovascular system. The physical exam should involve a number of imaging tests to search for suspicious cell formation.
Medical Imaging Tools
X-rays: Chest or abdomen x-rays can reveal fluid build-up, masses, or signs of non-cancerous pleural disease. Radiology imaging sometimes will not pick up evidence of diffuse cancerous growths on the mesothelium, but will readily produce a shadow created by a single tumor that may occur more readily with peritoneal mesothelioma.
Computed Tomography (CT) Scan: A tomography is an exam that creates images of cross-sections or layers of the body, producing images that can more easily detect abnormalities at a given depth within the body. CT scans can locate pleural disease, chest wall invasions, and can also be used to guide fine needle aspiration tests. However, CT scans cannot differentiate between benign or malignant mesothelioma.
Magnetic Resonance Imaging (MRI): MRI scans use a computer-linked magnet to photograph details of the inside of the body and can determine the severity of a tumor – but cannot determine whether the growth is cancerous or not. One of the more common benign forms of pleural affliction is the growth of pleural plaques on the mesothelium. These are small, benign growths that calcify over time and while they can be a precursor to malignant mesothelioma, often are a condition that remains static over time and has no serious health implication.
Positron Emission Tomography (PET): PET imaging tests have become one of the most efficient ways of diagnosing mesothelioma tumors as well as determining the staging of the cancer. This technology uses an analysis of biological processes to produce a three dimensional image that is capable of identifying cancer cells. The radioactive tracer isotope used in the procedure includes glucose, which can flag cancer cells because of their accelerated use of glucose. PET scans are capable of analyzing the molecular structure of certain cells in this fashion, which results in the ability to perform a preliminary analysis of the extent, or spread of these cells.
While medical imaging technology continues to become more productive for diagnostic purposes with tumors and diffuse malignant conditions such as pleural mesothelioma, imaging alone cannot produce a confirmed diagnosis. PET imaging can provide an analysis of the degree of malignancy and in some cases can differentiate between malignant and benign cells. In some cases it can provide additional analysis of a condition identified by a CT scan. But generally a confirmation of malignant mesothelioma requires a biopsy, an analysis of fluid from pleural or peritoneal effusion, or both.
Pathology Tools for Diagnosing Mesothelioma
Biopsy: A tissue biopsy is the most direct method of identifying the nature of abnormal cells. For pleural mesothelioma, retrieval of a biopsy sample may require minor surgery allowing for an extraction of tissue between the ribs. A peritoneal sample may be obtained through a laparoscopy procedure complemented with a tissue extraction tool.
Extraction of Effusion Fluids: Pleural effusion is a common symptom of pleural mesothelioma. Effusion refers to the excess buildup of fluids in the area where mesothelioma cancer is actively developing and in fact it occurs with all three principal forms of mesothelioma: pleural, peritoneal, and pericardial. Extraction of a fluid sample can generally be achieved through the use of a long needle and perhaps an endoscope into the thoracic cavity or the peritoneum. The value of a fluid sample is the ability to search for evidence of malignant cells. While a fluid sample is another adjunct procedure and not conclusive, it is a valuable part of the diagnostic protocol.
- Problems in Mesothelioma Diagnosis, Histopathology, January 2009, Addis et al., http://www3.interscience.wiley.com/cgi-bin/fulltext/121532060/HTMLSTART
- PET for the Evaluation of Pleural Thickening Observed on CT, Journal of Nuclear Medicine, 2004, Kramer et al
- Mesothelioma- VATS Biopsy…, European Journal of Cardio-Thoracic Surgery, 1999, Grossebner et al, http://ejcts.ctsnetjournals.org/cgi/content/full/16/6/619?maxtoshow=&hits=10&RESULTFORMAT=&author1=+Grossebner&fulltext=mesothelioma+biopsy&searchid=1&FIRSTINDEX=0&sortspec=relevance&resourcetype=HWCIT
- Soluble Mesothelin in Effusions: a useful tool for the Diagnosis of Malignant Mesothelioma, Thorax, March 2007, Creaney et al, http://thorax.bmj.com/content/62/7/569.abstract