Mesothelioma

Mesothelioma is a disease because of the growing and the divide abnormally and uncontrolled of mesothelium cells. The growth will invade and damage tissues and organs around it. Mesothelium is a membrane that covers and protects most of internal organs. The most of the abnormal growth is in Pleura, the membrane that cover the lung, most of because of asbestos.

There are three major histological type of mesothelioma: sarcomatous, epithelial and mixed. Pleural mesothelioma usually begins as discrete plaques and nodules that coalesce to produce a sheetlikeneoplasm. Tumor growth usually begins at the lower part of the chest. The tumor may invade the diaphragm and encase the surface of the lung and interlobar fissures.

The tumor may also grow along drainage and thoracotomy tracts. As the disease progresses, it often extends into the pulmonary parenchyma, chest wall, and mediastinum. Pleural mesothelioma may extend into the esophagus, ribs, vertebra, brachial plexus, and superior vena cava.

Asbestos, amphibole asbestos, asbestos-crocidolite, and amosite asbestos in particular, is the principal carcinogen implicated in the pathogenesis. Exposure to chrysotile asbestos is associated with a lower incidence of mesothelioma. The industries associated with asbestos exposure include mining, ship building involving the use of asbestos, asbestos cement manufacture, ceramics, paper milling, auto parts (asbestos brake lining), railroad repair, and insulation. In Turkey, the use of the fibrous substance erionite (similar to amphibole asbestos) in building construction has led to an epidemic of pulmonary mesothelioma. Environmental exposure to asbestos in areas polluted by the substance may increase the incidence of mesothelioma.

Most malignant mesotheliomas have complex karyotypes, with extensive aneuploidy and rearrangement of many chromosomes. A loss of a single copy on chromosome 22 is the most common abnormality.

Causes:

·          A substantial proportion of patients were exposed to asbestos in asbestos mills, shipping yards, mines, or their homes.

·          The crocidolite in asbestos is associated with mesothelioma in miners, manufacturers (using asbestos), and heating and construction workers. The rod-shaped amphiboles are more carcinogenic than the chrysotile.

·          Malignant mesothelioma has also been linked to therapeutic radiation using thorium dioxide and zeolite, a silicate in the soil.

·          An etiological role for simian virus 40 in malignant mesothelioma has also been suggested. Asbestos exposure alone was associated with malignant mesothelioma, but simian virus 40 alone was not; thus, some epidemiological evidence exists that simian virus 40 is a possible cocarcinogen. Its direct role at this point is still controversial.

·          Interleukin 8 has direct growth-potentiating activity in mesothelial cell lines.

·          Loss of one copy of chromosome 22 is the single most common karyotypic change in malignant mesothelioma. Other chromosomal changes commonly observed include 1p, 3p, 9p, and 6q. Several changes in the tumor suppressor gene p16 (CDKN2A) and p14 (ARF) and loss of function of neurofibromin 2 (NF2) or merlin are altered.

Symptoms of mesothelioma may not appear until 30 to 50 years after exposure to asbestos. Shortness of breath and pain in the chest due to an accumulation of fluid in the pleura are often symptoms of pleural mesothelioma. Symptoms of peritoneal mesothelioma include weight loss and abdominal pain and swelling due to a buildup of fluid in the abdomen. Other symptoms of peritonealmesothelioma 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.

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 athoracoscopy. 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.

Treatment for mesothelioma depends on the location of the cancer, the stage of the disease, and the patient's age and general health. Standard treatment options include surgery, radiation therapy, andchemotherapy. Sometimes, these treatments are combined.

Surgery is a common treatment for mesothelioma. The doctor may remove part of the lining of the chest or abdomen and some of the tissue around it. For cancer of the pleura (pleural mesothelioma), a lung may be removed in an operation called a pneumonectomy. Sometimes part of the diaphragm, the muscle below the lungs that helps with breathing, is also removed.

Radiation therapy, also called radiotherapy, involves the use of high-energy rays to kill cancer cells and shrink tumors. Radiation therapy affects the cancer cells only in the treated area. The radiation may come from a machine (external radiation) or from putting materials that produce radiation through thin plastic tubes into the area where the cancer cells are found (internal radiation therapy).

Chemotherapy is the use of anticancer drugs to kill cancer cells throughout the body. Most drugs used to treat mesothelioma are given by injection into a vein (intravenous, or IV). Doctors are also studying the effectiveness of putting chemotherapy directly into the chest or abdomen (intracavitary chemotherapy).

To relieve symptoms and control pain, the doctor may use a needle or a thin tube to drain fluid that has built up in the chest or abdomen. The procedure for removing fluid from the chest is calledthoracentesis. Removal of fluid from the abdomen is called paracentesis. Drugs may be given through a tube in the chest to prevent more fluid from accumulating. Radiation therapy and surgery may also be helpful in relieving symptoms.