What is Malignant Mesothelioma?

• How did I get it?
• Tumor Locations
• Cell Types
• Orphan Disease

How easy is it to get Mesothelioma?

About 3,000 Americans are diagnosed with this cancer each year, according to the U.S. Centers for Disease Control and Prevention. The typical latency period (time between exposure to asbestos and visible symptoms) can range from 15 to over 50 years. One study published in The Annals of Occupational Hygiene in 2003 analyzed 796 cases of asbestos-related disease found that latency period was about three years less for asbestosis vs mesothelioma. Patients with latency periods of less than 20 years were extremely rare, accounting for only 3 percent of asbestosis cases and 2 percent of mesothelioma cases.

How did I get Mesothelioma?

It is caused by exposure to asbestos. Asbestos is a fiber that was once widely used hundreds of building industrial, commercial and housing products and is still present in millions of U.S. workplaces and homes. The disease does not appear for at least 15 years after exposure to asbestos. The risk of exposure to asbestos — and the risk of malignant mesothelioma – remain a very real danger.

Cause of the Cancer

Exposure to asbestos, a group of microscopic mineral fibers, is the cause of this cancer. There are six sub-classification of asbestos: actinolite, amosite, anthophyllite, chrysolite, crocidolite, and tremolite. Asbestos, the commercial name given to these fibers, was a valuable material in several industries, particularly steel manufacturing and shipyards, in the early to mid-20th century. Asbestos easily separates when handled, causing microscopic particles to be released into the air that are subsequently inhaled by anyone in the vicinity. A vast majority of people diagnosed with mesothelioma were exposed to asbestos on job sites.

Types and locations of tumors

Mesothelioma is so-named because it affects the mesothelium (or mesothelial membrane), a layer of cells covering body cavities and internal organs. The mesothelium is comprised of mesothelial cells, which provide a protective surface and play a role in a number of processes such as fluid transport, inflammation and tissue repair. The mesothelium lines the pleural, peritoneal and pericardial cavities as well as the testicles. When asbestos fibers are inhaled or ingested they can enter the mesothelium and injure the mesothelial cells, eventually giving rise to malignant mesothelioma tumors.

Pleural Mesothelioma

The most common type is pleural mesothelioma, which affects the pleura — the mesothelial membrane lining the lungs and chest wall. Mesothelioma that begins in the pleura typically result from asbestos fibers being inhaled. Tumors that develop in the pleura may spread to the nearby diaphragm, heart, and blood vessels of the chest. Early symptoms of pleural mesothelioma can include shortness of breath, pleural effusion (fluid buildup), chest pain, cough, and a lack of energy.

Peritoneal Mesothelioma

When it develops in the peritoneum, the mesothelial membrane that covers the abdominal cavity and the organs within it, is called peritoneal mesothelioma (or abdominal mesothelioma). Peritoneal is the second most common form of this cancer, accounting for about 10-15% of new diagnoses, and may result from swallowing asbestos fibers or inhaling fibers that then work their way into the abdomen. Patients with the peritoneal type often experience abdominal swelling due to fluid buildup accompanied by abdominal pain, weight loss, and loss of appetite.

Pericardial Mesothelioma

The pericardium is the mesothelial membrane covering the heart. Pericardial mesothelioma is a highly lethal and very rare form of mesothelioma, accounting for roughly 1-5% of all new cases. Fluid in the pericardial space, shortness of breath, fever, chest pain, weight loss, and heart palpitations are symptoms of pericardial mesothelioma.

Testicular

The rarest of all types, mesothelioma of the tunica vaginalis testis (testicular mesothelioma) is a tumor of the membrane covering the testicle. Because of its rarity, there is little clinical agreement about testicular mesothelioma characteristics and symptoms, making diagnosis extremely difficult. Patients sometimes report painful swelling of the testicle and a doctor diagnoses the cancer intra-operatively (during surgery) or post-operatively, following laboratory analysis. Ultrasound and other diagnostic imaging may also be used for diagnosis.

Signs and Symptoms

Mesothelioma symptoms often start out like other respiratory diseases such as the flu, pneumonia or COPD. However, anyone with a history of asbestos exposure should seek medical attention immediately if he or she exhibits these symptoms:

• Shortness of breath
• Chest pain
• Pleural effusion (fluid on the lungs)
• Weight loss
• Persistent cough
• Loss of appetite

Treatment

This is one of many cancers that is still considered incurable and it is difficult to treat, because it is:

• Very aggressive
• Fast-growing
• Usually diagnosed in the late stages

Many treatments focus on maximizing life expectancy and decreasing the pain and symptoms associated with the disease. Patients may undergo surgery, chemotherapy or radiation therapy. The treatments are primarily based on methods used for other cancers. There are some rays of hope for mesothelioma sufferers — with the success of recent research, new treatments have been developed that specifically target mesothelioma. Targeted therapies take advantage of the unique genetic characteristics of the patient, and personalized treatments allow doctors to select an approach that is most effective for each patient.

Cell Types

Mesothelioma cells are grouped into three main categories: epithelioid, sarcomatoid (fibrous), and biphasic (mixed). Epithelioid is by far more the most common, while sarcomatoid is the least diagnosed and most difficult to treat. Each case is unique and there is no one-size-fits-all treatment. The stage of the disease and where the tumor is located are the two most important factors when determining treatment options. More aggressive treatments can be applied to epithelioid cells due to a better prognosis than sarcomatoid and biphasic cases. A second opinion is recommended for all patients diagnosed with sarcomatoid and biphasic mesothelioma. An accurate diagnosis is the key to getting the best and proper treatments.

Epithelioid

Doctors have done the most research on this type of cells because it is the most commonly diagnosed. Epithelial cells line most organs in the body. They act as protective barriers, while also playing a role in the secretion of fluids and sensory perception. A thoracoscopy is usually administered to identify malignant epithelial cells. Tissue samples are then taken from the tumor for further evaluation. There are several subtypes of epithelial cells, including adenoid, cystic, signet ring, and poorly differentiated. Cystic epithelial cells are normally located in the peritoneum, while poorly differentiated cells are generally in the pleural lining.

Sarcomatoid

This cell type is difficult to diagnose not only because its rare, but also because it looks similar to several other cell types. Sarcomatoid mesothelioma is very aggressive and has an unfavorable prognosis. Nodules formed within sarcomatoid tumors attack fat and the parietal pleura tissue surrounding it. This process looks very similar to fibrosarcoma tumors under a microscope, which can lead to misdiagnosis. Malignant sarcomatoid cells, like fibrous histiocytoma, can have more than one nucleus, which can lead to misdiagnosis. Sarcomatoid mesothelioma is highly resistant to most available treatments. It is vital to get an accurate diagnosis as early as possible to keep options open.

Biphasic

Patients with malignant epithelioid and sarcomatoid cells present are diagnosed with biphasic mesothelioma. The prognosis for this type of cell is better than sarcomatoid but worse than epithelioid cases. Those who have more malignant epithelial cells present will have more treatment options and a better prognosis. Diagnosis is extremely difficult due to the small tissue samples taken from biopsies. Biphasic cells also looks very similar to other types of cancers, particularly carcinosarcomas and synovial sarcomas.

Orphan Disease

This type of cancer is known as an orphan disease in the United States. An orphan or rare disease status is assigned to a disease or disorder if it affects fewer than 200,000 Americans at any given time. The U.S. Food and Drug Administration estimates that 25 million people are affected by more than 6,000 rare diseases. According to the National Organization for Rare Disorders, 1 out of 10 Americans have a rare disease. It is diagnosed in 3,000 Americans each year and shares the orphan disease distinct with other well-known diseases including multiple sclerosis, AIDS, and cerebral palsy. According to government statistics, between 85 to 90 percent of orphan diseases are serious or life-threatening, yet only about 200 of them currently have any effective treatments. But there is hope. The government and pharmaceutical companies pursue effective treatments for rare disease sufferers. In 2012, the U.S. National Institutes of Health and the European Commission joined forces to form the International Rare Disease Research Consortium. That group is committed “to the development of 200 new rare disease treatments by the year 2020 and the development of diagnostics for all rare disorders.”