Diagnosis

Proper diagnosis of mesothelioma requires a combination of physical, radiological and pathological examinations, as well as the taking of an accurate history including potential asbestos exposure. The most common physical symptoms of mesothelioma are shortness of breath, chest pain, unproductive cough, weight loss and loss of energy. Because these symptoms are common to many illnesses, mesothelioma often goes undetected as doctors look to more common causes of the symptoms. For this reason, it is important to raise the doctor’s level of suspicion for mesothelioma by making sure that the history of asbestos exposure is revealed in the admission questionnaire or during the history taken by the doctor or nurse.

Presented with the combination of these symptoms and a history of asbestos exposure, doctors will frequently order radiological testing such as an X-ray, CT scan, PET scan or MRI. Abnormalities revealed in any of these studies, such as a pleural effusion (excess fluid in the pleural linings of the lungs) or a suspected mass, should prompt additional testing.

 

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CT Scans

A CT scan — also called CT, computerized tomography or CAT scan — is an X-ray technique that produces images of internal organs that are more detailed than those produced by conventional X-ray exams.

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PET Scans

A positron emission tomography (PET) scan is a unique type of imaging test that helps doctors see how the organs and tissues inside the body are actually functioning.

The test involves injecting a very small dose of a radioactive chemical, called a radiotracer, into the vein of your arm. The tracer travels

through the body and is absorbed by the organs and tissues being studied. A machine then scans the body and detects and records the energy given off by the tracer substance and, with the aid of a computer, this energy is converted into three-dimensional pictures. A physician can then look at cross-sectional images of the body organ from any angle in order to detect any functional problems.

A PET scan can measure such vital functions as blood flow, oxygen use, and glucose metabolism, which helps doctors identify abnormal from normal functioning organs and tissues. The scan can also be used to evaluate the effectiveness of a patient’s treatment plan, allowing the course of care to be adjusted if necessary.

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Effusions/Cytology

Diagnosis of diseases based on examination of individual cells and small clusters of cells, called cytology or cytopathology, has become increasingly important in cancer diagnosis.

For patients with a pleural effusion, a thoracentesis (drainage of the fluid) will typically be performed to ease the pressure exerted on internal organs and reduce discomfort. A sample of the fluid will be examined by a pathologist for malignant cells. However, given the high rate of “false negative” fluid cytology results for mesothelioma, experienced doctors will typically proceed with a tissue biopsy even if the fluid cytology is negative.

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Tissue Biopsy

The only reliable test for diagnosing mesothelioma is a tissue biopsy, or removal of a small piece of tissue for laboratory examination. There are several different types of biopsies. A needle (percutaneous) biopsy removes tissue using a hollow tube called a syringe. A needle is passed thru the syringe into the area of concern. The tissue is taken out using this needle. Needle biopsies are often performed using x-rays (usually CT scan), which guide the surgeon to the appropriate area.

An open biopsy is a surgery that uses general anesthesia. This means you are asleep and pain-free during the procedure. The procedure is done in a hospital operating room. A surgeon makes a cut into the affected area, and the tissue is removed.

Closed biopsy uses a much smaller surgical cut than open biopsy. The small cut is made so that a camera-like instrument can be inserted. This instrument can be used to see the area, and helps guide the surgeon to the appropriate place to take the sample. Examination of the biopsy samples includes immunohistochemical (IH) staining in which the pathologist looks for specific signs, or markers, of mesothelioma. This is often a complex process which requires analysis by a pathologist who is experienced in diagnosing mesothelioma and the specific cell types of the disease (epithelial, sarcomatoid, desmoplastic, biphasic). It is not uncommon even for experienced pathologists to seek a second opinion when diagnosing mesothelioma.

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Staging

When mesothelioma is diagnosed, the doctors want to learn the stage of the disease. Staging is a process

used by physicians to describe the extent of the disease or how advanced the cancer is. Staging assists the physician in determining the likely course of the cancer and how it may respond to different treatments (also known as the prognosis of the disease).

Knowing the stage of the disease helps the doctor plan an appropriate treatment approach and evaluate the results of different interventions. Different staging systems are used for different types of cancer.

CT scans and MRI’s are often used to determine whether the cancer has spread.

A mediastinoscopy can help show whether the cancer has spread to the lymph nodes in the chest. Using a lighted viewing instrument, called a scope, the doctor examines the center of the chest (mediastinum) and nearby lymph nodes. In mediastinoscopy, the scope is inserted through a small incision in the neck; in mediastinotomy, the incision is made in the chest. In either procedure, the scope is also used to remove a tissue sample.

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Mesomark

MESOMARK, a manual enzyme-linked immunosorbent assay (ELISA), is a new method of diagnosing mesothelioma. It works by identifying serum tumor markers called soluble mesothelin-related peptides (SMRP). These proteins are released into the bloodstream by malignant mesothelioma cells. FDI’s mesothelioma assay is a two-step immunoassay that quantitates SMRP in human blood using a standard ELISA microplate sandwich assay format.