Mesothelioma Lung Cancer

As the world moves forward, urbanizes and aims for a more progressive and modernized living, a rising disease has came to its verge of popularity. Mesothelioma lung cancer starts to bewilder the public. Different questions were raised: What is this Mesothelioma lung cancer and how does one acquires this rare form of cancer?

Mesothelioma lung cancer is one of the uncommon yet serious type lung cancers. It is s a malignant type of cancer which affects the tissue linings of the lungs. This arises from the Mesothelium, which is composed of thin layers of tissues called Parietal and Visceral membranes. These cover most body organs and cavities including the lungs, abdominal organs, and heart. Mesothelium has different names depending on the organ that it protects. For the lungs, it is called the pleura while for the heart and abdomen, it is called the pericardium and peritoneum respectively. These structures allow the organs to move freely, glide easily and prevent friction which causes damage and injury to the organs.

In a Mesothelioma lung cancer, the mesothelium undergoes abnormal changes causing its cells to uncontrollably multiply. This disorderly growth of cells may lead to metastasis, which is the spread and invasion of the cancer cells to different sites, adjacent organs or even distant organs of the body. Most common sites affected are the pleura and the peritoneum.

Studies have shown that one of the most common identified risk factor for this serious type of lung cancer is the exposure to Asbestos. Asbestos is a group of naturally occurring fibrous minerals that had been popularly used for commercial purposes. This type of mineral came from two different mineral groups called Serpentine and Amphobile. These types of mineral fibers are fine and flexible with high tensile strength, difficult to tear, and are virtually indestructible by any chemical or biolgical process. These are commonly found on industrial and domestic products such as cement, shingles, fireproof paint, brake linings, roof coatings, flooring products, and asbestos clothing. The hazardous occupational and environmental exposure is one of the most identified factors of developing this type of cancer. Majority of these individuals who develop Mesethelioma acquire this through direct exposure: by being exposed to asbestos dust while on the job; or indirect exposure: by being exposed to asbestos fibers found on the clothes from someone who has worked in areas where asbestos dust was found.

The diagnosis of Mesothelioma lung cancer, however, can be very difficult because the disease may undergo a latency stage which means that it would take decades for the symptoms to begin to appear and by that time, the cancer is already within its advanced stages. Several tests are used in diagnosing Mesotheliomia. These include chest x-ray, CT scan, MRI scan, and a biopsy. These tests will help in determining the condition of the lungs and its cells. Upon the the diagnosis, the doctor will also do a complete physical examination and a medical history to determine prior exposure of the patient to asbestos. The common signs and symptoms of Mesothelioma depend on its location. Most of these patients experience difficulty in breathing or shortness of breath, chest pain, and generalized fatigue. However, acute pain will be more evident in the chest for pleural and pericardial mesothelioma, and in the abdominal region for peritoneal mesothelioma.

Treatment includes different types of surgery, radiation therapy, and chemotherapy. The National Cancer Institute (NCI) is now sponsoring research studies for the discovery of new treatment for this type of cancer. Nonetheless, the reduction from these occupational and environmental exposures to these toxic substances can still be the most effective way of preventing this deadly type of cancer to upset the mankind.

Types of Mesothelioma

Mesothelioma can be classified into two major groups, benign and malignant. Malignant mesothelioma is organized into four main categories based on the location of the tumor: Rarely mesothelioma is diagnosed in both the pleural and peritoneal cavity but may be found more often as the disease process progresses.

1. pleural – found in the chest cavity, on the surface of the lung and on the diaphragm,
2. peritoneal – found in the abdomen on the surface of the omentum and visceral organs,
3. pericardial – growing on the exterior surface of the pericardium, or lining of the heart, and
4. testicular – noted as a thickening of the ducts and glands in the testes.

Each of these categories of mesothelioma is further divided into one of three subtypes, epithelial, sarcomatoid or mixed. Among the total spectrum of asbestos patients there are a smaller number of cases with different cancers, such as lung cancer and metastatic cancer of the liver, kidneys, bones and other organs. (m) In addition, sarcomatous varieties have been judged to be extremely aggressive, and can be associated with intracranial metastases – brain tumors. There are also benign mesothelial proliferations and well differentialed papillary mesothelioma that are of low malignant potential.  The diagnosis should be confirmed by an experienced pathologist as in many cases a more virulent form of the disease can be mixed in with this seemingly benign process.  In most cases these tumors are of low malignant potential and are treated only when they begin to cause symptoms and most often with surgery as a single modality. http://www.curemeso.org

There are 2 main types of mesothelioma

    * Mesothelioma in the covering of the lung (pleural mesothelioma)
    * Mesothelioma in the abdomen (peritoneal mesothelioma)

Pleural mesothelioma starts in the sheets of tissue that cover the lungs. Peritoneal mesothelioma grows in the tissue lining the inside of the abdomen (tummy). Pleural mesothelioma is much more common than peritoneal mesothelioma.

Between 67 and 75% of mesothelioma cases are pleural mesothelioma. Peritoneal mesothelioma is much less common, making up between 25 to 33% of cases.

Mesothelioma is also grouped according to how the cells look under a microscope. There are 3 types

    * Epithelioid - between 5 and 6 out of 10 cases (50 to 60%)
    * Sarcomatoid or fibrous - around 1 in 10 cases (10%)
    * Mixed type (also called biphasic type) - between 3 and 4 out of 10 cases (30 to 40%)

These types of mesothelioma cells can be further divided into other types called

    * Clear cell
    * Small cell
    * Acinar cell
    * Tubopapillary cell

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A History of Mesothelioma

The history of the acceptance of mesothelioma as a primary malignancy of the pleura is one of more than 100 years of confusion and frustration. The disease was rare enough that its appearance was only intermittently identified in the medical literature. With less than one case in a thousand being identified as pleural or peritoneal carcinomas, it is little wonder that physicians at first were reluctant to assign it the status of a primary tumor. The medical establishment of the 1800’s was convinced that pleural tumors had to be metastatic cancers from some other primary tumor, regardless of the lack of evidence for this.

In the late 1800’s it was noted that mesothelioma could be found in the lymph nodes and the theory developed that the cancer began in the lymphatic system and spread to the lungs or abdomen. Not until 1891 was consideration given to the opposite theory. As always, research into the nature of mesothelioma was hampered by the lack of a sufficiently large body of evidence. Patients, thankfully, were still few and far between and reaching a consensus with so little clinical data was difficult.

The early 20th century finally brought acceptance that some pleural sarcomas could arise even without a primary cancer elsewhere in the body. From this humble beginning, the realization that the tumor developed from the mesoderm hit home and the term mesothelioma came to be accepted in 1921. Through the ‘30’s and ‘40’s further research and an increasing number of patients established the description of the tumor and began to identify the link to asbestos exposure.

Because of the confusion over whether mesothelioma truly was a separate clinical entity, five different views about causation took hold:

1. The endothelial lining of the lymph nodes was the cause, hence the name endothelioma.
2. Aberrant lung tissue became malignant within the lining of the pleura.
3. The tumor arose in the pleural capillary endothelium.
4. Tumors of epithelial origin always arose from a primary tumor elsewhere. The primary tumors were felt to be too small to be detected in autopsy.
5. The tumor arose from the mesothelial lining of the pleura and peritoneum.

It was Wedler in 1943 who reported a connection too high to be coincidental between asbestosis and pleural malignancy in a population of German asbestos workers. The analysis, which factually reported the connection but made no attempt to stamp the disease with a label, was widely accepted in Germany and ignored in the rest of the world. It wasn’t until the early 1950’s that additional evidence rescued the observations of Wedler and began to build an irrefutable connection between asbestos exposure and mesothelial cancer.http://www.curemeso.org

What Causes Mesothelioma?

The exact method by which asbestos causes mesothelioma isn’t known with certainty. Animal models have provided some understanding of the type of damage that asbestos fibers can do, but the exact mechanism hasn’t been found yet. After asbestos became a commercially successful product, it was soon apparent that asbestos workers were an at-risk population.

Starting at the turn of the century, British investigators discovered a relationship between exposure to high levels of asbestos and respiratory disease. These early studies were often suppressed by government at the request of the asbestos industry. By the mid 50’s American medical researchers had joined the chorus of concerned professionals identifying asbestos as hazardous. Much of their work was never published or was suppressed and/or disputed by scientists in the pay of the asbestos lobby.

Figure 3: Amphiboles Protruding, Brook T. Mossman, UVM College of Medicine.

Asbestos fibers have been detected in many resected surgical specimens from mesothelioma patients. In pleural mesothelioma, asbestos fibers are found trapped in the tissues from the lower parts of the lung and they are sometimes concentrated into nodules or spots on the parietal pleura, the primary location for mesothelioma in the thoracic cavity. These fibers are found using electron beam microscopy. They are invisible to the naked eye and are not routinely commented upon in a typical pathology report. Although smoking while exposed to asbestos is known to significantly increase lung cancer risks, smoking is not a risk factor in the formation of mesothelioma.  It is not uncommon to find pleural plaques in the lungs of patients with primary peritoneal mesothelioma which is indicative of heavy asbestos exposure.

Genetic susceptibility may also contribute to the cause of malignant mesothelioma. Populations of three small villages located in Turkey has been environmentally exposed to a rare asbestos-like fiber called erionite for generations.

50% of all deaths in these villages was attributable to malignant mesothelioma. All villagers lived in homes built with this mineral and research by Dr. Michele Carbone discovered that those who developed mesothelioma had a genetic predisposition  to the disease . Predisposed individuals who lived in villages without erinote were not found to develop mesothelioma. Further research into the residents of these communities has confirmed an autosomal dominant pattern of susceptibility to malignant mesothelioma and disease develops in the presence of asbestos-like fibers.

from : www.curemeso.org

What Is Mesothelioma?

Mesothelioma is a cancer of the smooth lining of the chest, lungs, heart, and abdomen. This skin layer is made up of mesothelial cells, hence the name mesothelioma. Mesothelioma is a diffuse but solid tumor that begins as a result of insult to the tissues caused by asbestos particles. These have penetrated into the pleural cavity of the chest or into the abdomen. Mesothelioma is either called pleural mesothelioma or peritoneal mesothelioma based on where it appears.

Because it occurs in such a small number of patients mesothelioma is often referred to as an orphan disease. Numbers of newly affected individuals in the United States have been reported to be between 2,500 and 3,000 every year. A steady rise in cases is reported in North America, Europe, Australia, and Asia.

In its early stages mesothelioma is difficult to detect as it may start with a thickening of the pleural rind, or fluid which can be associated with many other conditions. This rind is normally thin and smooth in the non diseased state. In time it begins to demonstrate progression forming a more pronounced irregular rind and nodules which coalesce into a crust that compresses and invades into adjacent structures compromising lung and cardiac function. In the abdominal cavity it can invade into the liver and bowel rendering the patient inoperable. Peritoneal mesothelioma it is often found coating the omentum described sometimes as a salt like sand like particles too numerous to count and impossible to remove without sacrificing the entire omentum. Involvement of the ovaries and fallopian tubes is not uncommon in women and often mesothelioma is confused with ovarian cancer. Once vital organs are involved or disease identified outside of the operative field surgery is no longer an option and patients are referred to chemotherapy or clinical trials.

Figure 1: Right Pleural Epithelial Mesothelioma on chest wall and lung. Photo courtesy K. Brauch

For the vast majority of patients, as the tumor mass grows, once subtle symptoms will give way to weight loss, cough, respiratory infections, fatigue, shortness of breath, digestive and bowel problems and pain in the chest or abdomen, depending upon whether it is pleural or peritoneal. It may begin to weep fluid into the intracavitary space. In the chest cavity this is called an effusion and it fills the space where the lobes of the lung reside, next to the lining of the chest cavity, and often spreads into the area surrounding the heart creating symptoms similar to those observed in congestive heart failure. In peritoneal patients it is called ascites and it fills the abdomen bathing the visceral organs with this malignant fluid.

Figure 2: Epithelial mesothelioma on the diaphragm. Photo courtesy K. Brauch.

The symptoms gradually become more noticeable prompting the patient to seek a medical consultation. By this time the progression of the disease may already be too advanced as the tumor may have spread to the lymph nodes and/or begun to metastasize to remote organs of the body like the brain, spleen, liver or kidneys. Metastatic mesothelioma is considered late stage and incurable, given the current state of treatments. It is widely reported that only 10-20% of patients with pleural mesothelioma are diagnosed early enough for surgical intervention, the rest are referred on to palliative care No such figures have been reported in peritoneal mesothelioma.