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Diagnosis is the process of finding the cause of a health problem. The process of diagnosis may seem long and frustrating, but it is important for the doctor to rule out other reasons for a health problem before making a cancer diagnosis. Diagnostic tests for mesothelioma cancer are usually done when:
- the symptoms of mesothelioma are present
- the doctor suspects mesothelioma after talking with a person about their health and completing a physical examination
Many of the same tests used to initially diagnose cancer are used to determine the stage (how far the cancer has progressed). Your doctor may also order other tests to check your general health and to help plan your treatment. Tests may include the following.
The medical history is a record of present symptoms, risk factors and all the medical events and problems a person has had in the past. The medical history of a person’s family may also help the doctor to diagnose mesothelioma.
In taking a medical history, the doctor will ask questions about:
- a personal history of
- occupational exposure to asbestos
- living with someone who works with asbestos
- previous treatment with radiation therapy to the chest or abdomen
- signs and symptoms that may suggest mesothelioma
A physical examination allows the doctor to look for any signs of mesothelioma. During a physical examination, the doctor may:
- examine the lungs by listening with a stethoscope
- tap the chest to hear percussion sounds
- look at the motion of the chest during breathing
- check the face and neck for swelling
- feel the abdomen for any lumps and look for swelling
- feel for any enlarged lymph nodes
An x-ray uses small doses of radiation to make an image of the body’s structures on film. It is used to check for abnormalities of the lung or abdomen.
- A chest x-ray can show problems with the lungs, such as thickening of the pleura or fluid around the lung (pleural effusion), because of pleural mesothelioma.
- An x-ray of the abdomen may be done to find out the cause of abdominal symptoms.
Ultrasound uses high-frequency sound waves to make images of structures in the body. An abdominal ultrasound may be done to check for fluid in the abdomen if the doctor suspects peritoneal mesothelioma.
A CT scan uses special x-ray equipment to make 3-dimensional and cross-sectional images of organs, tissues, bones and blood vessels inside the body. A computer turns the images into detailed pictures. It is used to:
- determine if mesothelioma is present and to find its location
- A CT scan is the main imaging test used to assess both pleural and peritoneal mesothelioma.
- help guide the doctor when taking a biopsy
- assess the extent of mesothelioma and whether it has spread
- help make decisions about treatment
MRI uses powerful magnetic forces and radio-frequency waves to make cross-sectional images of organs, tissues, bones and blood vessels. A computer turns the images into 3-dimensional pictures. It is used to:
- determine if mesothelioma is present and to find its location
- assess the extent of mesothelioma and whether it has spread, especially if surgery is being considered
- help make decisions regarding treatment
During a biopsy, tissues or cells are removed from the body so they can be tested in a laboratory. The pathology report from the laboratory will confirm whether or not cancer cells are present in the sample. The biopsies that could be used to diagnose mesothelioma are:
- A hollow needle (or small tube) is inserted through the skin and between the ribs into the pleural cavity to remove fluid so that it can be examined under a microscope.
- A thoracentesis is also done to reduce a buildup of fluid in the pleural cavity (pleural effusion) because of pleural mesothelioma.
- A hollow needle (or small tube) is inserted through the skin into the abdominal cavity to remove fluid, so that it can be examined under a microscope.
- A paracentesis is also done to reduce a buildup of fluid in the abdominal cavity (ascites) because of peritoneal mesothelioma.
- endoscopic biopsy
- A variety of endoscopic procedures may be done to take samples of fluid or tissues to check for pleural or peritoneal mesothelioma.
- open biopsy
- Sometimes doctors need to do a more invasive procedure, a surgical biopsy, to get a large enough sample of tissue to make a diagnosis.
- A thoracotomy is surgery to open the chest cavity. It allows the surgeon to remove a larger sample of tissue or a tumour from the chest.
- A laparotomy is surgery to open the abdominal cavity. It allows the surgeon to remove a larger sample of tissue or a tumour from the abdomen.
An endoscopic procedure may be done to diagnose and stage a mesothelioma. It allows a doctor to look inside body cavities using a flexible tube with a light and lens on the end (an endoscope). Endoscopic procedures that may be done for mesothelioma are:
- A thoracoscopy may be done to examine the chest cavity, including the pleura, and take samples of tissue to diagnose and stage pleural mesothelioma.
- This procedure may also involve video-assisted thoracic surgery (VATS) to obtain biopsy samples.
- A mediastinoscopy may be done to examine the mediastinummediastinumThe space in the chest between the lungs, breastbone and spine that contains the heart, great blood vessels, thymus, trachea (windpipe), esophagus and lymph nodes. in the chest and take samples of tissue from lymph nodes in the chest. The samples can be examined under a microscope to stage pleural mesothelioma and decide if surgery is an option.
- endobronchial ultrasound (EBUS)
- An endobronchial ultrasound (EBUS) may also be done to take a biopsy sample from lymph nodes in the mediastinum.
- A bronchoscopy is done with an ultrasound probe attached to the bronchoscope. This allows the doctor to look inside the bronchibronchiThe large tubes, or airways, that branch off from the windpipe (trachea) into the lungs, where they branch into smaller tubes (bronchioles) that end in the alveoli (air sacs). Bronchi carry air to and from the lungs. and lungs, see if any nearby lymph nodes look suspicious and remove biopsy samples from the lymph nodes.
- A laparoscopy is a procedure that allows the doctor to look inside the abdomen and take biopsy samples. The surgeon makes a small cut through the abdomen and inserts an endoscope, called a laparoscope.
- This procedure may be done to examine the abdominal cavity and take samples of tissues or fluid within the abdomen to diagnose and stage peritoneal mesothelioma.
- A laparoscopy may also be done to stage pleural mesothelioma to see if the cancer has spread into the diaphragm.
A complete blood count (CBC) measures the number and quality of white blood cells, red blood cells and platelets. A CBC is done to check for problems with platelets and white blood cells. People with mesothelioma can have an abnormally high platelet level (thrombocytosis) and high white blood cell level (leukocytosis).
Blood chemistry tests measure certain chemicals in the blood. They show how well certain organs are functioning and can also be used to detect abnormalities.
Doctors may use blood chemistry tests to determine a prognosis for people with mesothelioma. People with mesothelioma may have an increased lactate dehydrogenase (LDH). LDH is an enzyme in the blood that can be increased when there is tissue damage or if cancer cells are present.
Tumour markers are substances – usually proteins – in the blood that may indicate the presence of mesothelioma. Tumour marker tests are used to check a person’s response to cancer treatment. Tumour markers are not used to diagnose mesothelioma, but increased levels may help confirm a diagnosis of malignant mesothelioma.
The tumour markers that may be measured in people with mesothelioma are:
- soluble mesothelin-related peptides (SMRPs)
These markers appear to be sensitive for mesothelioma, but studies are being done to better determine their role in diagnosing mesothelioma and assessing response to treatment.
Pulmonary function tests (also called lung function tests) check how well the lungs are working. They measure how much air the lungs can hold and how well the person can let the air out of the lungs. This type of test is important if surgery is being considered as a treatment for mesothelioma.
A PET scan uses radioactive materials (radiopharmaceuticals) to detect changes in the metabolic activity of body tissues. A computer analyzes the radioactive patterns and makes 3-dimensional colour images of the area being scanned. It is used to see if mesothelioma has spread to distant sites in the body, if other imaging tests are not conclusive and if surgery is being considered.
Sometimes a combined PET/CT scan may be done. It joins CT scans and PET scans into one procedure. A PET/CT may provide a more complete picture of a tumour’s location and growth than either test alone. PET scan and PET/CT are not as readily available as other imaging tests and are only available in certain centres in Canada.
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