Mesothelioma shares symptoms with many other, less serious conditions, so a doctor will try to rule out those conditions through a physical exam including x-rays and tests of lung function. Imaging tests such as MRIs , CAT scans and PET scans may be done.
The only way to definitively diagnose mesothelioma is through analysis of tissue taken from the mesothelium through biopsy. The biopsy can be done by inserting a camera and surgical instruments through a small incision (thoracoscopy in the chest or laparoscopy in the abdomen) or by opening up the abdominal or chest cavity (thoracotomy or laparotomy). The tissue sample will be examined through a microscope to detect patterns that differentiate it from benign cells or other types of cancerous cells. If diagnosis is still unclear, tests for different chemicals in the cells or genetic testing of the cells may be needed, or an electron microscope can offer a closer look at the cells.
When a patient presents to a physician complaining of difficulty breathing, abdominal pain or pneumonia-type symptoms and reports a history of asbestos exposure, an x-ray or CT scan is ordered to detect the presence of asbestos in or around the lungs, heart or stomach. If asbestos is detected, the physician will look for signs of tumors around vital organs. If tumors are detected, the patient will be referred for further tests to determine if there is a diagnosis of mesothelioma.
These tests are performed in one of two ways, depending upon the condition of the patient. A needle biopsy is a minimally invasive procedure in which cells from the affected area are abstracted through a hollow needle. A more precise test is to perform an “open biopsy”, in which a small piece of tissue is surgically removed for biopsy. After samples are sent to pathology, and if mesothelioma is present, it will then be determined if the disease is benign or malignant.
A thorough medical history may reveal exposure to asbestos in the past or the presence of suspicious symptoms. Physical examination is followed by x-rays of the affected area of the body (lungs, heart, or abdomen). Positive x-rays signal the need for a CT scan (computerized tomography) or MRI (magnetic resonance imaging) for a detailed analysis of body structures. When the location of the abnormal cells is known, biopsies are taken. Biopsy of lung tissues is done by thoracotomy since the tumor affects the outer lung surface. Abdominal biopsies are obtained via laparoscopy. In both cases, small incisions allow the surgeon to visualize the internal organs and to take tissue for pathological examination.
Surgery is often needed to determine the staging of the disease. This reveals whether the tumor is self-contained or has spread to adjacent structures or other more remote areas of the body. This information can then guide treatment.
Mesothelioma is often difficult to diagnose because the symptoms are so similar to other conditions such as lung cancer and other types of cancers. The first step in diagnosis is to conduct a thorough physical examination. The physician also will gather a lengthy medical history, including questions related to possible asbestos exposure. An X-ray will provide an image of the lungs or abdomen showing any abnormal changes. Furthermore, a CT scan (computed tomography) will produce more detailed pictures of areas inside the body using a computer rather than film. An MRI (magnetic resonance imaging) provides a three-dimensional, detailed view of the areas where mesothelioma is suspected. The MRI can differentiate mesothelioma from other lung tumors and determine its location and size. However, the most definitive test is a biopsy (tissue sample) of the affected tissues to provide information regarding the strength and rate of growth of the tumor.
Diagnosing mesothelioma involves both imaging tests and biopsies. Imaging tests, which may include x-rays, CT scans, and/or MRI scans, are usually the first step in making a preliminary diagnosis.
If an imaging test indicates the possibility that mesothelioma may be present, the next step is to perform a biopsy. Biopsies involve collection of tissue to be examined by a pathologist. A needle biopsy involves extracting tissue via a hollow needle inserted into the chest cavity. This is the least invasive, but also the least conclusive biopsy technique. A surgical biopsy involves making an actual incision for the purpose of collecting tissue for examination.
The tissue is then examined by a pathologist, who checks for the presence of malignant cells is the sample.
The following are methods used to diagnose mesothelioma:
Chest X-ray – will show an abnormal fluid build-up within the pleural cavity, called a pleural effusion. Another sign may include a mass or calcification near or in the pleural lining.
Computed Tomography (CT) Scan – will confirm a pleural effusion. It will also give the exact location and measurement of a mass or suspected tumor. Another sign may include thickening of the pleural lining (usually greater than 1 cm.)
Computed Tomography & Positron Emission Tomography Scan (CT/PET) – combined exams that will show the extent of the malignant disease. This is a test which evaluates the biological function of the malignancy to determine the “stage” of the disease.
Fine needle aspiration – a tissue or fluid sample is collected using a thin needle. The sample is thin viewed under a microscope to determine whether it’s malignant (cancerous) or benign (non-cancerous).
Mesothelioma is diagnosed using a patient’s history and physical, radiographic studies, and pathologic examination of tissue.
Key components in the patient’s history are exposure to asbestos and complaints relating to fluid build up or a mass, such as pain or shortness of breath. Patients often undergo tests to rule out other conditions, as early symptoms tend to be non-specific.
Radiographic studies include plain films, CT, MRI, or PET, of the chest and abdomen.
Chest x-rays may show effusion, thickening, calcifications, scarring, or a chest mass. CT scans can help guide needle biopsy. MRI can reveal lymph node or diaphragm involvement. PET is now considered the gold standard for staging the disease. These studies are often used in combination for diagnosis, staging, and treatment decisions.
Pathologic examination of the tissues involved confirms a suspected diagnosis. Tissue is removed from the affected site and studied microscopically for evidence of cancer cells.
The use of a combination of testing is needed for proper diagnosis of mesothelioma because it can be easily confused with other carcinomas of the lung as well as other diseases. Chest x-ray is often the first line in diagnostic studies and may show obliteration of the diaphragm and thickening of the pleura, however, it is not specific for mesothelioma. Computed tomography (CT) is more helpful in distinguishing tumor characteristics and the extent of infiltration in to the pleura and will show irregular pleural nodular thickening. Magnetic resonance imaging (MRI) with gadolinium-based contrast material may be useful in defining the extent of penetration into the diaphragm and chest cavity. Thoracoscopic biopsies are necessary to confirm the diagnosis and have 98% specificity for mesothelioma.
• Chest x-ray
-A chest x-ray can reveal a pleural effusion when more than 300 mL of fluid is present in the pleural cavity.
-Other signs of pleural mesothelioma that can be seen on a chest x-ray include pleural calcifications, thickening of the pleural, or an irregular pleural-based mass.
• CT and MRI
-They are used to determine the tumor burden, demonstrate pleural thickening, assess enlargement of lymph nodes, and to identify effusions.
• Tests of tissue and fluid samples
-Thorancetesis is used to obtain pleural fluid, if an effusion is present.
-Thoracoscopy can be used to sample a pleural or pericardial tumor.
-Laproscopy is used to see and obtain a biopsy of a peritoneal tumor.
-Mediastinoscopy allows for biopsy and visualization of the lymph nodes.
• Electron microscopy
-The distinction between malignant mesothelioma and benign inflammatory conditions may be difficult. Electron microscopy can be confirmatory.
Symptoms of early mesothelioma are very general and often ignored as a serious pathological process. Most patients do not have serious symptoms until two to three months prior to a mesothelioma diagnosis. Since the most common area affected are the lungs the most common symptoms tends to involve the respiratory tract. Symptoms of pleural mesothelioma may include: shortness of breath, cough, weakness, weight loss, and hoarseness.
The easiest type of test is a chest x-ray combined with a good history from the patient. The only difficulty with a chest x-ray is that it is not very specific in telling whether a process is malignant or benign. The most common sign on an x-ray is thickening of the lining of the lungs. CT scans are often the first test to reveal mesothelioma and its extent. The test that confirms the diagnosis of mesothelioma is a biopsy. A biopsy requires sample of tissue to be removed from the body and examined under microscope by a pathologist.