Malignant mesothelioma (pronounced "mez-o-theel-e-oh-ma"), also known as "asbestos cancer," is a rare form of cancer found in the lining of the heart, lungs, abdomen, or the internal reproductive organs. This lining is called the mesothelium and is where mesothelioma gets its name.

Because tumors of the mesothelium are rarely benign (non cancerous), cancerous malignant mesothelioma is usually referred to simply as "mesothelioma," or in casual terms simply "meso."

The mesothelium covers various organs in the body protecting them and allowing organs to move against each other as the lungs expand and contract or the heart beats. Where the mesothelium covers the internal organs, it is called the visceral mesothelium and where it covers the body walls, it is called the parietal mesothelium.

Malignant mesothelioma occurs when cells within the mesothelium become abnormal and divide uncontrollably. If not caught early enough, the cancer may metastasize, spreading to other organs of the body. While it is a very aggressive form of cancer, several treatment options are available for malignant mesothelioma.

The only known cause of mesothelioma is asbestos. Because asbestos exposure is the only known cause of mesothelioma, it is sometimes referred to as "asbestos cancer." However, malignant mesothelioma is not the only cancer caused by asbestos. Exposure to asbestos can also cause laryngeal, colon, and lung cancer.

There is no known safe level of asbestos exposure, but asbestos cancers are dose dependent, meaning those exposed for longer periods of time and to greater amounts of asbestos are more likely to develop asbestos-related disease. If you were exposed to asbestos, you should tell your physician so he or she can make a determination for appropriate testing based on your history of exposure and symptoms.

One of the earliest descriptions of malignant mesothelioma was written in 18701, although the tumor was referred to as tuberkelhnliche lymphadenome ("tubercle-like" lymphadenoma) in this early, German-language review. It wasn't until the start of the 19th century that tumors arising out of the mesothelium were named mesotheliomas. The process of appropriately identifying, and thus naming, mesothelioma was not without some debate, confusion, and even controversy.

In an article that would help define the modern ideas on the pathology and diagnosis of mesothelioma, Klemperer and Rabin's 1930 "Primary Neoplasms of the Pleura: A Report of Five Cases" noted that thirty different names had been used to describe the neoplasms being studied:

The names applied most frequently, endothelioma, endothelial carcinoma, carcinoma, sarcoma, lymphangitis proliferans, sarcocarcinoma and mesothelioma, are indicative of the different morphologic pictures and the different opinions of the authors as to the point of origin. To make this confusion more complete, there have been included in the literature on primary tumors of the pleura a number of cases that, on critical examination, are proved to originate definitely in the lungs or in the bronchi."2

Even as late as 1943the year many consider asbestos was determined a cause mesothelioma (see Wedler, below)researchers suggested "pleuroma" as a name for these tumors3, however, mesothelioma gradually became the accepted term. Likely as a result of relative rarity of mesothelioma, the connections between asbestos and mesothelioma began to be made even as mesothelioma itself was still not well understood or identified.

In 1933, London pathologist Steven Roodhouse Gloyne published a study in which he discussed the movement of asbestos fibers through the lymph system and the particularly high concentrations of asbestos that collected in the lymph nodes in the central chest in a person with asbestosis4. Two years later, in 1935, Gloyne is considered the first to make a possible connection between occupational asbestos exposures and mesothelioma.

Gloyne described malignancies arising from the pleura of an asbestosis victim5, noting that "at the moment" there was no indication that the tumor correlated to the asbestosis present. However, in 1938, when the German government began to recognize and compensate lung cancer as an occupational disease of asbestos workers, mesothelioma was included as a compensable respiratory cancer.

What is often regarded as the first study to connect mesothelioma with asbestos was published in 1943 by German researcher, Dr. H.W. Wedler6. Wedler reviewed a collection of autopsy records belonging to asbestosis victims, his results revealing an excess of both lung and pleural malignancies. Also of interest in Wedler's study, was his observation of an often a long interval between exposure and the development of cancer and his assertion that these diseases must be regarded as occupational.

Several more publications in a similar vein followed, and throughout the 1940s and 1950s, articles discussing asbestosis cases often mentioned accompanying lung cancers and/or mesotheliomas. In 1954, F. Leicher reported the first case of peritoneal mesothelioma in an asbestos textile factory spinner7. Many researchers, physicians, and other specialists believe the causal relationship between asbestos and mesothelioma was, or at least could, have been established by the mid-1950s. (Interestingly, even as late as 1955, some studies did not refer directly to "mesothelioma," but to a malignancy of the pleura or similar.)

It was an article published by South African researchers J.C. Wagner, Christopher Sleggs, and Paul Marchand that is generally attributed as the removing any doubts that asbestos causes mesothelioma. Wagner had initially been hired by the South African Government Mining Engineer to study occupational diseases, namely, asbestosis; however, Wagner began to focus his attention on the unusual pleural tumors he was finding during his research. It was not a decision the mining industry in South Africa was happy about, as they were busy investing in new operations to meet the growing global demands for asbestos.

The study, first presented at a conference in Johannesburg in 1959 and published in 1960 in the British Journal of Medicine, detailed 33 cases of mesothelioma with all but one case having a proven asbestos exposure history. In eight cases, their exposure history was occupational, however, some twenty of the mesothelioma cases discussed simply lived as infants near the mines.

Although the language of Wagner's study left the association between asbestos and mesothelioma "possible," the results of such damaging evidence against asbestos in occupational and, perhaps more importantly, bystander asbestos exposures was not lost on the industry. Partly as a result of pressures from industrial interests, Wagner left South Africa in 1962 for a new position in the UK. Any lingering doubts about asbestos' tie to mesothelioma left open by Wagner were shortly quieted by several studies which further confirmed the link.

In the 50s and 60s, New Jersey physician Irving J. Selikoff saw several men suffering from pulmonary abnormalities as a result of inhaling asbestos dust on the job at the Patterson, NJ UNARCO (Union Asbestos & Rubber Company) plant. UNARCO's specialty was in producing asbestos insulation materials for the US Navy. When several of Selikoff's UNARCO patients died as a result of cancer, he contacted UNARCO requesting their participation in a study of workers' health.

When UNARCO declined, Selikoff tried a different tactic. If the makers of the insulation were being injured by asbestos, Selikoff supposed, those installing it might face similar risks. Early in 1962, Selikoff contacted the International Association of Heat & Frost Insulators & Asbestos Workers (New York Local 12 and Newark Local 32). The union officials were, in fact, quite concerned about workers' health. So much so, that they had contacted the Industrial Hygiene Foundation (IHF) about them several years prior. Originally called the Air Hygiene Foundation, the IHF was almost wholey industry-funded, so their responses to the union's concerns were, not surprisingly, reassurances about the safe handling of asbestos insulation materials.

Over the course of the next year, Selikoff examined more than a thousand insulators, performing pulmonary function tests and administering x-rays. Selikoff finally presented his findings in 1964 at the New York Academy of Science sponsored conference 'Biological Effects of Asbestos.' His results were staggering. Among the insulators, mortality was 25% higher than was expected, and not from asbestosis alone, but from lung cancer, stomach cancer, colon cancer, rectal cancer, colorectal cancer, and malignant mesothelioma.

Along with Selikoff's presentation at the 1964 conference, Wagner and other researchers presented further evidence of the connection between asbestos and mesothelioma. British physician Molly Newhouse echoed Wagner's own findings when she presented her research regarding mesothelioma cases among people who lived near, but were not employed by, a London asbestos factory. Many of the presentations emphasized that victims often did not suffer long or heavy exposures, work with asbestos, nor have asbestosis.

In 1968, the British Medical Journal asserted that "at the end of 1965, it was clear that asbestos workers [were] at special risk of developing cancers of at least two typebronchial carcinoma and mesothelioma."

Last update: December 03, 2015. 02:54:51 pm.

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