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.

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:

Mesothelioma Damaged Lungs

• 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.

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. A history of exposure to asbestos may increase clinical suspicion for mesothelioma. A physical examination is performed, followed by chest X-ray and often lung function tests. The X-ray may reveal pleural thickening commonly seen after asbestos exposure and increases suspicion of mesothelioma. A CT (or CAT) scan or an MRI is usually performed. If a large amount of fluid is present, abnormal cells may be detected by

Mesothelioma Affected Cell

If cytology is positive or a plaque is regarded as suspicious, a biopsy is needed to confirm a diagnosis of mesothelioma. A doctor removes a sample of tissue for examination under a microscope by a histopathologist. 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 laparoscopy. To obtain tissue for examination, the doctor makes a
small opening in the abdomen and inserts a special instrument into the abdominal cavity. If these procedures do not yield enough tissue, more extensive diagnostic surgery may be necessary.

The Culprit: Asbestos

Types of asbestos and associated fibers:

• Chrysotile (white asbestos)
• Amosite (brown asbestos)
• Crocidolite (blue asbestos)
• Anthophyllite (gray asbestos)

White Asbestos - Chrysotile, CAS No. 12001-29-5, is obtained from serpentine rocks. Chrysotile is the type most often used industrially in the United States. There is evidence that this type of asbestos is harmful, although not perhaps as harmful as other forms (refer to UK Health & Safety Commission report Asbestos: Effects on health of exposure to asbestos, 1985). One formula given for Chrysotile is Mg3(Si2O5)(OH)4.

Brown Asbestos - Amosite, CAS No. 12172-73-5, is a trade name for the amphibole known as Grunerite, from Africa, named as an acronym from Asbestos Mines of South Africa. One formula given for Amosite is Fe7Si8O22(OH)2.

Blue Asbestos - Riebeckite, CAS No. 12001-28-4, also known under the variety name of Crocidolite, is an amphibole from Africa and Australia. It is the fibrous form of the amphibole riebeckite. Blue asbestos is commonly thought of as the most dangerous type of asbestos. One formula given for Crocidolite is Na2Fe2+3Fe3+2Si8O22(OH)2.

Notes: chrysotile commonly occurs as soft friable fibers. Asbestiform amphibole may also occur as soft friable fibers but some varieties such as amosite are commonly straighter. All forms of asbestos are fibrillar in that they are composed of fibers with widths less than 1 micrometer that occur in bundles and have very long lengths. The asbestiform amphiboles are generally thought to be more carcinogenic than chrysotile because of their durability in the lung. Amphiboles most commonly occur in nature in a safer nonfibrous form. Asbestos with particularly fine fibers is also referred to as "amianthus".

Other asbestos minerals, such as tremolite asbestos, CAS No. 77536-68-6, Ca2Mg5Si8O22(OH)2; actinolite asbestos (or smaragdite), CAS No. 77536-66-4, Ca2(Mg, Fe)5Si8O22(OH)2; and anthophyllite asbestos, CAS No. 77536-67-5, (Mg, Fe)7Si8O22(OH)2; are less commonly used industrially but can still be found in a variety of construction materials an insulation materials and have been reported in the past to occur in a few consumer products. In 1989, In the United States, the Environmental Protection Agency (EPA) passed the Asbestos Ban and Phase Out Rule which was subsequently overturned in 1991. This ruling leaves many consumer products that can still legally contain trace amounts of asbestos.