Diagnosis

Diagnosing mesothelioma is often difficult, because the symptoms are similar to those of a number of other conditions. Diagnosis begins with a review of the patient’s medical history, including any history of asbestos exposure. A complete physical examination may be performed, including x-rays of the chest or abdomen and lung function tests. A CT (or CAT) scan or an MRI may also be useful. A CT scan is a series of detailed pictures of areas inside the body created by a computer linked to an x-ray machine. In an MRI, a powerful magnet linked to a computer is used to make detailed pictures of areas inside the body. These pictures are viewed on a monitor and can also be printed.

A biopsy is needed to confirm a diagnosis of mesothelioma. In a biopsy, a surgeon or a medical oncologist (a doctor who specializes in diagnosing and treating cancer) removes a sample of tissue for examination under a microscope by a pathologist. A biopsy may be done in different ways, depending on where the abnormal area is located. If the cancer is in the chest, the doctor may perform a thoracoscopy. In this procedure, the doctor makes a small cut through the chest wall and puts a thin, lighted tube called a thoracoscope into the chest between two ribs. Thoracoscopy allows the doctor to look inside the chest and obtain tissue samples. If the cancer is in the abdomen, the doctor may perform a peritoneoscopy. To obtain tissue for examination, the doctor makes a small opening in the abdomen and inserts a special instrument called a peritoneoscope into the abdominal cavity. If these procedures do not yield enough tissue, more extensive diagnostic surgery may be necessary.

If the diagnosis is mesothelioma, the doctor will want to learn the stage (or extent) of the disease. Staging involves more tests in a careful attempt to find out whether the cancer has spread and, if so, to which parts of the body. Knowing the stage of the disease helps the doctor plan treatment.

Mesothelioma is described as localized if the cancer is found only on the membrane surface where it originated. It is classified as advanced if it has spread beyond the original membrane surface to other parts of the body, such as the lymph nodes, lungs, chest wall, or abdominal organs.

source : National Cancer Institute

Signs and Symptoms

Symptoms of mesothelioma may not appear until 20 to 50 years after exposure to asbestos. Shortness of breath, cough, and pain in the chest due to an accumulation of fluid in the pleural space are often symptoms of pleural mesothelioma.

Symptoms of peritoneal mesothelioma include weight loss and cachexia, abdominal swelling and pain due to ascites (a buildup of fluid in the abdominal cavity). Other symptoms of peritoneal mesothelioma may include bowel obstruction, blood clotting abnormalities, anemia, and fever. If the cancer has spread beyond the mesothelium to other parts of the body, symptoms may include pain, trouble swallowing, or swelling of the neck or face.

These symptoms may be caused by mesothelioma or by other, less serious conditions.

Mesothelioma that affects the pleura can cause these signs and symptoms:

chest wall pain
pleural effusion, or fluid surrounding the lung
shortness of breath
wheezing, hoarseness, or cough

In severe cases, the person may have many tumor masses. The individual may develop a pneumothorax, or collapse of the lung. The disease may metastasize, or spread, to other parts of the body.

Tumors that affect the abdominal cavity often do not cause symptoms until they are at a late stage. Symptoms include:

abdominal pain
ascites, or an abnormal buildup of fluid in the abdomen
a mass in the abdomen
problems with bowel function
weight loss

In severe cases of the disease, the following signs and symptoms may be present:

blood clots in the veins, which may cause thrombophlebitis
disseminated intravascular coagulation, a disorder causing severe bleeding in many body
organs
jaundice, or yellowing of the eyes and skin
low blood sugar level
pleural effusion
pulmonary emboli, or blood clots in the arteries of the lungs
severe ascites

A mesothelioma does not usually spread to the bone, brain, or adrenal glands. Pleural tumors are usually found only on one side of the lungs.

How does asbestos cause mesothelioma?

Asbestos is made up of tiny fibres. You can breathe these fibres in when you come into contact with asbestos. The fibres work their way into the pleura, lining the lung. They irritate the pleura and damage the cells that the pleura are made of. Some of the fibres that have been breathed in can be coughed up and swallowed. This is probably the cause of peritoneal mesothelioma.

If you have been exposed to asbestos, your family may also have been exposed. Asbestos fibres can be carried home on your clothes. Research studies have confirmed that the family of people exposed to asbestos also have a higher risk of developing mesothelioma.

Asbestos is the name of a group of minerals that occur naturally as masses of strong, flexible fibers that can be separated into thin threads and woven. Asbestos has been widely used in many industrial products, including cement, brake linings, roof shingles, flooring products, textiles, and insulation. If tiny asbestos particles float in the air, especially during the manufacturing process, they may be inhaled or swallowed, and can cause serious health problems. In addition to mesothelioma, exposure to asbestos increases the risk of lung cancer, asbestosis (a noncancerous, chronic lung ailment), and other cancers, such as those of the larynx and kidney.

source: Cancer Research UK & Wikipedia, the free encyclopedia

What is asbestos and SV40?

Asbestos

Asbestos is an insulating material that is heat and fire resistant. In the past, asbestos was used widely in the :

1. Building industry
2. Ship building industry
3. Manufacture of household appliances
4. Motor industry

So most cases of mesothelioma occur in men who have worked in manufacturing using asbestos or used asbestos products, particularly in construction or engineering. The use of asbestos was very heavy in the years after the war (after 1945). Mesothelioma may not develop until 15 - 40 years after you have been exposed to asbestos, which is why we are seeing an increase in cases now. The number of cases is expected to peak around 2018 and then start to decline.

There are three types of asbestos: blue, brown and white. Blue and brown asbestos are linked with mesothelioma. They have been banned since the late 1980's and cannot be imported into the UK. White asbestos is now also thought to be harmful. The use of all asbestos was banned in 1999 in the UK.


The SV40 virus

There has been some research into a virus called SV40 (the SV stands for 'simian virus'). There is a lot of dispute amongst scientists about this and it isn't generally accepted as a cause. It seems more likely that the virus doesn't cause mesothelioma. It is possible that SV40 may help to increase risk if you've been exposed to another more major risk factor. Doctors call this a 'co-factor'. But SV40 certainly hasn't been proved to be a co-factor so far. In any case, it is far less important a risk factor than asbestos.

source : Cancer Research UK

What are the risk factors for mesothelioma?

Working with asbestos is the major risk factor for mesothelioma. A history of asbestos exposure exists in almost all cases. However, mesothelioma has been reported in some individuals without any known exposure to asbestos. In rare cases, mesothelioma has also been associated with irradiation, intrapleural thorium dioxide (Thorotrast), and inhalation of other fibrous silicates, such as erionite.

The combination of smoking and asbestos exposure significantly increases a person's risk of developing cancer of the airways (lung cancer, bronchial carcinoma). The Kent brand of cigarettes used asbestos in its filters for the first few years of production in the 1950s and some cases of mesothelioma have resulted. Smoking current cigarettes does not appear to increase the risk of mesothelioma.

Some studies suggest that simian virus 40 (SV40) may act as a cofactor in the development of mesothelioma.

What is the Mesothelium and Mesothelioma ?

Mesothelium

The mesothelium is a membrane that covers and protects most of the internal organs of the body. It is composed of two layers of cells: One layer immediately surrounds the organ; the other forms a sac around it. The mesothelium produces a lubricating fluid that is released between these layers, allowing moving organs (such as the beating heart and the expanding and contracting lungs) to glide easily against adjacent structures.

The mesothelium has different names, depending on its location in the body. The peritoneum is the mesothelial tissue that covers most of the organs in the abdominal cavity. The pleura is the membrane that surrounds the lungs and lines the wall of the chest cavity. The pericardium covers and protects the heart. The mesothelial tissue surrounding the male internal reproductive organs is called the tunica vaginalis testis. The tunica serosa uteri covers the internal reproductive organs in women.

Mesothelioma

Mesothelioma (cancer of the mesothelium) is a disease in which cells of the mesothelium become abnormal and divide without control or order. They can invade and damage nearby tissues and organs. Cancer cells can also metastasize (spread) from their original site to other parts of the body. Most cases of mesothelioma begin in the pleura or peritoneum.

Mesothelioma is a form of cancer that is almost always caused by previous exposure to asbestos. In this disease, malignant cells develop in the mesothelium, a protective lining that covers most of the body's internal organs. Its most common site is the pleura (outer lining of the lungs and chest cavity), but it may also occur in the peritoneum (the lining of the abdominal cavity) or the pericardium (a sac that surrounds the heart).

Most people who develop mesothelioma have worked on jobs where they inhaled asbestos particles, or have been exposed to asbestos dust and fibre in other ways, such as by washing the clothes of a family member who worked with asbestos, or by home renovation using asbestos cement products. There is no association between mesothelioma and smoking.

source: National And Cancer Institute & Wikipedia, the free encyclopedia.