Mesothelioma

Mesothelioma is a rare and aggressive cancer that forms in the mesothelium—a thin, protective membrane that lines the chest cavity, abdominal organs, heart, and testes. Its job is to help these organs move smoothly against each other by producing a lubricating fluid.

There are different types of mesothelioma depending on where the tumors form, but they all share one overwhelming cause: exposure to asbestos.

Asbestos fibers are microscopic, sharp, and nearly indestructible. When inhaled or swallowed, they can become lodged in the mesothelium—where they remain for decades. Over time, these fibers cause inflammation, scarring, and genetic damage that can eventually lead to cancer.

Learn more about how asbestos causes mesothelioma to develop.

Although it's very rare today, mesothelioma was virtually nonexistent before asbestos was widely used. In a review of over 2,000 autopsies conducted at New York’s Mount Sinai Hospital between 1883 and 1910—before asbestos became common in construction or industry—not a single case of mesothelioma was found. That changed dramatically in the 20th century as asbestos was added to thousands of products and workers were exposed without warning. ¹

Bottom line: Mesothelioma is not a random disease. It is overwhelmingly the result of asbestos exposure—often decades before diagnosis.

Where Can Mesothelioma Occur?

Mesothelioma can develop in any part of the body lined by a mesothelium—a specialized membrane that forms during early embryonic development. The word mesothelioma literally means “cancer of the middle lining,” because the mesothelium originates from the mesoderm, one of the three primary layers of the embryo (alongside the endoderm and ectoderm).

These linings serve a vital function: they allow internal organs to move smoothly against each other. But they also present a vulnerable surface—particularly when asbestos fibers become lodged in the tissue.

There are four primary types of mesothelioma, each named for the part of the body where it begins:

• Pleural Mesothelioma – forms in the pleura, the lining around the lungs. This is the most common type, accounting for 75–90% of all mesothelioma cases. Learn more →

• Peritoneal Mesothelioma – develops in the peritoneum, which lines the abdominal cavity. About 10–15% of mesothelioma cases fall into this category. Learn more →

• Pericardial Mesothelioma – occurs in the lining around the heart. It’s extremely rare and often diagnosed late. Learn more →

• Testicular Mesothelioma – arises in the tunica vaginalis, the mesothelial lining of the testicles. Fewer than 1% of cases are testicular. Learn more →

Although the location may differ, the cause is nearly always the same: exposure to asbestos. Whether inhaled into the lungs or carried to other parts of the body through the bloodstream or lymphatic system, asbestos fibers can eventually lodge in the mesothelium and lead to cancer.

Wherever it starts, mesothelioma is almost always preventable—and almost always caused by someone’s failure to warn.

Types of Mesothelioma (By Cell Type)

In addition to identifying where mesothelioma occurs in the body, doctors classify the disease based on its histological subtype, which refers to the specific type of cells that make up the tumor. This classification is determined through microscopic examination of tissue samples, often obtained via biopsy. The microscopic details of the tumor's histology are critical because they influence the cancer's behavior, including its growth rate, likelihood of spreading, and resistance to therapy

There are three main histological types of mesothelioma:

Epithelioid Mesothelioma

Epithelioid mesothelioma is the most common histological subtype of malignant mesothelioma, accounting for approximately 50–70% of all diagnosed cases. This subtype is characterized by the presence of epithelioid cells, which tend to grow in organized and structured patterns. This organized growth pattern makes epithelioid mesothelioma more responsive to various treatment modalities, including surgery, chemotherapy, and immunotherapy. As a result, patients diagnosed with this subtype generally have the most favorable prognosis compared to other mesothelioma subtypes, such as sarcomatoid or biphasic mesothelioma. The relatively better outcomes associated with epithelioid mesothelioma highlight the importance of accurate histological diagnosis in guiding treatment decisions and predicting patient survival. ²

Learn more about epithelioid mesothelioma.

Sarcomatoid Mesothelioma

Sarcomatoid mesothelioma is a less common but highly aggressive subtype of malignant mesothelioma, accounting for approximately 10–20% of all cases. This form is characterized by spindle-shaped cells that exhibit a highly aggressive behavior, often spreading rapidly throughout the body. Unfortunately, sarcomatoid mesothelioma tends to resist most standard treatment options, including surgery, chemotherapy, and immunotherapy, making it particularly challenging to manage. Due to its aggressive nature and resistance to treatment, this subtype is associated with a significantly shorter survival time compared to other forms of mesothelioma, such as epithelioid or biphasic mesothelioma. These factors underscore the critical need for early diagnosis and innovative therapeutic approaches to improve outcomes for patients with this subtype.  ³

Learn more about sarcomaoid mesothelioma.

Biphasic (Mixed) Mesothelioma

Biphasic mesothelioma, also referred to as mixed mesothelioma, is a subtype that contains a combination of both epithelioid and sarcomatoid cells within the same tumor. The behavior and prognosis of biphasic mesothelioma largely depend on the relative dominance of these two cell types. Tumors with a higher proportion of epithelioid cells generally exhibit a better prognosis, as epithelioid cells are more responsive to treatment. Conversely, a greater presence of sarcomatoid cells is associated with a more aggressive disease course and poorer outcomes. This subtype accounts for approximately 20–30% of all mesothelioma cases, making it the second most common form after epithelioid mesothelioma. ⁴

Learn more about biphasic mesothelioma.

If you or your loved one has been diagnosed with mesothelioma, ask your doctor if the cell type is known. It can influence not just treatment options, but eligibility for clinical trials, prognosis expectations, and legal claims.

What Causes Mesothelioma?

Mesothelioma is one of the rarest cancers in the world—yet it has one of the clearest causes. Today, major public health authorities including the World Health Organization (WHO), Centers for Disease Control and Prevention (CDC), and NIOSH all agree: all types of asbestos—including chrysotile—can cause mesothelioma in both animals and humans.

In the United States, only 3,000 to 4,000 cases of mesothelioma are diagnosed each year. That low number is part of what makes the cause so striking. Before asbestos was widely used in American industries, mesothelioma didn’t appear at all. In a review of 2,276 consecutive autopsies performed at New York’s Mount Sinai Hospital between 1883 and 1910—decades before industrial asbestos use took off—not a single case of mesothelioma was identified. The disease simply didn’t exist in the population because the population simply wasn't exposed to asbestos.

That changed with the arrival of widespread asbestos use in the 20th century. Once hailed as a "magic mineral" due to its many unique properties, it is now known as a deadly carcinogen that should be avoided at all costs. But for most of the twentieth century, it wasn't possible to avoid asbestos because it was everywhere. Author Paul Brodeur explained in 1968: “[A]sbestos has become practically ubiquitous in modern society. There is not an automobile, airplane, train, ship, missile, or engine of any sort that does not contain asbestos in some form or other, and it has found its way into literally every building, factory, home, and farm across the land.”

Learn more about the six different minerals that we call asbestos.

Our modern understanding of mesothelioma’s cause can be traced back to the work of a young doctor in South Africa in 1960, whose research reshaped how the world viewed asbestos.

The Breakthrough: Wagner's Discovery in 1960

The first scientific breakthrough came in 1960, when South African pathologist Dr. Chris Wagner published a landmark study in the British Journal of Industrial Medicine. ⁶ Wagner documented an epidemic of mesothelioma among residents of the Cape Province, near crocidolite (blue asbestos) mines. Many of those affected had never worked directly with asbestos—they were family members, neighbors, or children simply living near mining operations.

What made Wagner’s study groundbreaking wasn’t just the data—it was the undeniable conclusion: brief, low-level, non-occupational exposure to asbestos could still cause mesothelioma. For the first time, scientists recognized that asbestos posed a community-wide health threat, not just an occupational hazard.

Wagner’s work sparked a wave of international research. Soon, doctors at Mount Sinai in New York and across Europe were finding similar cases in insulation workers, shipyard laborers, factory hands—and later, their families. The global medical consensus began to shift: asbestos caused mesothelioma, and no amount of exposure was safe.

Today it is widely accepted that if a person was exposed to asbestos and develops mesothelioma years after that exposure, the asbestos exposure is the most likely cause.

Today’s Medical Consensus on Mesothelioma

Today it is widely accepted that if a person was exposed to asbestos and develops mesothelioma years after that exposure, the asbestos exposure is the most likely cause. All major health authorities—including the World Health Organization, CDC, and NIOSH—agree.

The key factor that supports asbestos as a cause of a given person's mesothelioma is latency. In almost every asbestos-related case, mesothelioma develops 20 to 50 years after exposure - with some cases taking as long as 70 years. This long delay between exposure and disease onset is a signature feature of mesothelioma and one of the reasons it was so difficult to recognize as an occupational cancer for decades.

Even so, not every case of mesothelioma is caused by asbestos exposure. For example:

• Young children with mesothelioma may develop the disease due to inherited mutations, such as those in the BAP1 gene, which predispose them to cancer by impairing DNA repair mechanisms. In rare cases, however, the disease arises without a clear genetic or environmental cause, highlighting gaps in our understanding of mesothelioma's pathogenesis and the potential involvement of unknown factors.

• Therapeutic radiation, such as that used to treat Hodgkin lymphoma or other cancers, has been identified as a potential cause of mesothelioma when it damages the mesothelial cells lining the chest or abdomen. These radiation-induced cases often have a shorter latency period compared to asbestos-related mesothelioma, suggesting that the mechanisms of carcinogenesis may differ between these two exposures.

• And while genetic mutations like BAP1 can increase a person’s susceptibility to mesothelioma, by making their cells more vulnerable to damage, these mutations alone are not sufficient to cause the disease. Almost always, an environmental co-factor, such as asbestos exposure, is required to trigger the development of mesothelioma, with asbestos remaining the primary driver in the majority of diagnosed cases.

  • A person with a BAP1 mutation may be more susceptible to mesothelioma, but it’s the asbestos exposure that triggers the disease. The companies that exposed workers and consumers to asbestos are still fully liable—regardless of a person’s genetic vulnerability.This follows the same principle as the “eggshell skull” rule in tort law: if someone suffers serious injury because they were unusually fragile, you’re still responsible if your negligence caused the harm. Their condition doesn’t excuse your actions—it just explains the outcome. Or as shopkeepers sometimes put it: “You break it, you bought it.”

Debunking the SV40 Theory of Mesothelioma Causation

The Simian Virus 40 (SV40), a monkey virus that contaminated early polio vaccines between 1955 and 1963, was once suspected of increasing mesothelioma risk. This concern emerged after laboratory studies showed SV40 could transform human cells, and some researchers detected traces of the virus in mesothelioma tumor samples.

However, multiple large-scale epidemiological studies have since failed to find any reliable connection between SV40 and mesothelioma in human populations. A long-term cohort study comparing cancer rates in people who received SV40-contaminated vaccines to those who didn’t found no increased risk of mesothelioma or other cancers.

Further, it’s now understood that many of the original “positive” detections of SV40 were likely due to lab contamination or flawed testing methods, not genuine infections. As a result, SV40 is no longer considered a credible cause of mesothelioma by the medical community. ^{7 8}

The Bottom Line

If someone has mesothelioma and a history of asbestos exposure—even 50+ years ago—asbestos is almost certainly the cause.

In fact, it’s so strongly linked that mesothelioma is considered a “signal tumor” for asbestos exposure in epidemiology. People with high levels of exposure—such as construction workers, mechanics, refinery workers, or shipyard employees—are at especially high risk.

How Is Mesothelioma Diagnosed?

Mesothelioma can be difficult to diagnose—especially in its early stages. Its symptoms often resemble far more common conditions like pneumonia, COPD, or lung cancer, which means it is frequently misdiagnosed or dismissed until the disease has progressed.

Accurate diagnosis usually requires a combination of imaging, fluid testing, and a tissue biopsy, ideally at a medical center with experience in mesothelioma cases.

Imaging: The First Clue

Diagnosis often begins with a chest X-ray or CT scan, which may reveal abnormalities like pleural thickening, fluid buildup (pleural effusion), or suspicious masses. These imaging tests are typically the first step because they provide a quick and non-invasive way to look for signs of disease in the chest. While these findings can suggest the possibility of mesothelioma, they are not specific to the disease and cannot provide a definitive diagnosis on their own.

Additional imaging may include:

• PET-CT: Combines metabolic and structural imaging to detect active tumor growth or metastases. This advanced imaging technique uses a small amount of radioactive sugar to highlight areas of high metabolic activity, which are often associated with cancer. By combining this with detailed structural images, PET-CT can help identify not only the primary tumor but also whether the cancer has spread to other parts of the body.

• MRI: Offers superior detail when evaluating tumor invasion into the diaphragm or chest wall. Magnetic resonance imaging (MRI) uses powerful magnets and radio waves to create highly detailed images of soft tissues. This makes it particularly useful for assessing how far the tumor has spread into nearby structures, which is critical for planning surgery or other treatments.

• Ultrasound: Ultrasound: Often used to guide procedures like thoracentesis. Ultrasound uses sound waves to create real-time images of the chest, making it an excellent tool for guiding procedures like thoracentesis, where a needle is inserted to remove fluid from around the lungs. This helps ensure the procedure is both safe and effective by allowing doctors to precisely target the area of concern.

Fluid Testing (Thoracentesis)

In many mesothelioma cases, fluid collects in the pleural, abdominal, or pericardial cavity, depending on the type of mesothelioma. For peritoneal mesothelioma, paracentesis is used to drain fluid from the abdominal cavity, while for pericardial mesothelioma, a procedure called pericardiocentesis may be performed to remove fluid from around the heart. In rare cases of testicular mesothelioma, fluid buildup in the scrotum (hydrocele) may also be analyzed.

Doctors will look for cancer cells in the fluid—a process called cytology—but this test is often inconclusive. In pleural mesothelioma, for example, cytology detects cancer in fewer than 30% of cases. A tissue biopsy is almost always required for a definitive diagnosis.

Biopsy: The Gold Standard for Mesothelioma Diagnosis

A biopsy is the definitive method for diagnosing mesothelioma, as it involves removing a small sample of tissue for detailed microscopic examination. Unlike imaging or fluid testing, which can only suggest the presence of mesothelioma, a biopsy provides the conclusive evidence needed to confirm the disease. This critical procedure allows pathologists to:

• Confirm the diagnosis: By examining the tissue under a microscope, pathologists can identify the presence of malignant mesothelioma cells and distinguish them from other conditions that may mimic its symptoms.

• Determine the histological subtype (epithelioid, sarcomatoid, or biphasic): Identifying the specific subtype of mesothelioma is essential, as it influences both the prognosis and the choice of treatment options. For example, epithelioid mesothelioma generally has a better prognosis compared to the more aggressive sarcomatoid subtype.

• Perform specialized tests like immunohistochemical staining or genetic analysis: These advanced techniques help confirm the mesothelial origin of the tumor and differentiate it from other cancers, such as lung adenocarcinoma. Immunohistochemical staining uses specific antibodies to detect markers unique to mesothelioma, while genetic analysis can provide insights into mutations or molecular features that may guide targeted therapies.

Biopsies are a critical step in diagnosing mesothelioma, and the method used often depends on the suspected type of mesothelioma (pleural, peritoneal, pericardial, or testicular), the patient’s overall health, and the accessibility of the affected tissue. Below are the primary methods of biopsy, along with their relevance to specific mesothelioma types:

• VATS (Video-Assisted Thoracoscopic Surgery):
  This minimally invasive procedure is considered the most accurate method for diagnosing pleural mesothelioma. VATS allows surgeons to visually inspect the pleural cavity, obtain multiple tissue samples, and even perform additional procedures, such as pleurodesis, during the same session. It has a diagnostic sensitivity of up to 98%, making it the gold standard for pleural mesothelioma diagnosis. 

• CT-Guided Needle Biopsy:
  This less invasive method involves using computed tomography (CT) imaging to guide a needle to the suspected tumor site. While it is less invasive and may be more cost-effective, it often yields smaller tissue samples, which can limit its diagnostic accuracy. CT-guided needle biopsy is sometimes used for pleural mesothelioma but is generally less reliable for determining histological subtypes compared to VATS or open surgical biopsy. It may also be used for peritoneal mesothelioma when the tumor is accessible via imaging.

• Open Surgical Biopsy:
  In complex or ambiguous cases, an open surgical biopsy may be necessary. This method involves a more invasive surgical procedure, such as thoracotomy for pleural mesothelioma or laparotomy for peritoneal mesothelioma, to obtain larger and more comprehensive tissue samples. Open biopsies are particularly useful for accurately determining histological subtypes, as they provide more material for analysis. For example, open biopsies have been shown to allow accurate subtyping in 83% of cases, compared to 74% for VATS-guided biopsies.

• Pericardial Biopsy:
  For pericardial mesothelioma, a pericardial biopsy may be performed, often during a pericardiocentesis or open surgical procedure. This is a rare and challenging type of biopsy due to the location of the tumor and the limited amount of tissue that can be safely obtained.

• Testicular Biopsy:
  In cases of testicular mesothelioma, a biopsy of the affected testicular tissue is typically performed. This is usually done during surgery to remove the tumor or affected testicle, as testicular mesothelioma is extremely rare and often diagnosed incidentally.

Each biopsy method has its advantages and limitations, and the choice of technique is guided by the suspected mesothelioma type, the location of the tumor, and the need for accurate histological and molecular analysis.

Treatment Options for Mesothelioma

Treatment for mesothelioma depends on the location of the cancer, its stage, and the cell type. In general, doctors aim for multimodal therapy—a combination of surgery, chemotherapy, and immunotherapy—tailored to the individual. While mesothelioma is rarely curable, modern treatment strategies can extend survival, relieve symptoms, and improve quality of life.

Pleural Mesothelioma (Lungs)

Pleural mesothelioma is the most common form of the disease. Treatment may include pleurectomy/decortication (removal of the pleural lining), extrapleural pneumonectomy, chemotherapy (most often pemetrexed + cisplatin), and increasingly, immunotherapy with drugs like nivolumab and ipilimumab. Many patients also participate in clinical trials exploring new drug combinations and biomarkers.

Explore 2025 treatment options and survival rates for pleural mesothelioma →

Peritoneal Mesothelioma (Abdomen)

Peritoneal mesothelioma is treated very differently from the pleural type. The standard approach for eligible patients is CRS-HIPEC—cytoreductive surgery followed by heated chemotherapy directly infused into the abdominal cavity. This technique has significantly improved survival for many patients. Others may receive systemic chemotherapy or participate in emerging clinical trials.

Learn about modern treatments for peritoneal mesothelioma in 2025 →

Pericardial Mesothelioma (Heart)

Pericardial mesothelioma is rare and difficult to treat. Because it’s often diagnosed late, treatment typically focuses on palliative care to manage symptoms like chest pain and fluid buildup. In some cases, surgery to remove the tumor or relieve pressure on the heart may be possible, alongside systemic therapy.

See current treatment approaches for pericardial mesothelioma →

Testicular Mesothelioma (Tunica Vaginalis)

Testicular mesothelioma is the rarest form of the disease. Most patients undergo radical inguinal orchiectomy, sometimes followed by chemotherapy if the disease has spread. Because it’s often misdiagnosed as a benign condition like a hydrocele, early and accurate pathology is critical.

Read the 2025 treatment and prognosis guide for testicular mesothelioma →

Legal Action for Mesothelioma Victims

Mesothelioma is not a naturally occurring tragedy—it’s the direct result of corporate decisions made over decades. As early as the 1930s, asbestos manufacturers knew the material could cause deadly lung disease. By the 1940s and 1950s, internal documents show they were aware it could cause cancer. But rather than warn workers or the public, many companies concealed the risks to protect profits. Because it took decades for workers to get sick after being exposed, the asbestos industry got away with it for decades.

It took a dying insulation worker from Texas—Clarence Borel—to change that.

In 1973, Borel became the first person in American history to win a lawsuit proving that asbestos caused his mesothelioma and that the companies who exposed him were legally responsible. His case paved the way for thousands of others and exposed a cover-up that had lasted for decades.

Read the full story of Clarence Borel →

What Are Your Legal Options?

If you or a loved one has been diagnosed with mesothelioma, you may be entitled to compensation from multiple sources. These funds can help pay for treatment, cover lost income, and support your family.

Asbestos Trust Fund Claims

When asbestos manufacturers went bankrupt, they were required to create trust funds to compensate victims. These trusts still exist today and contain billions of dollars.

• You may qualify even if the exposure happened 50+ years ago.

• Most trust claims are paid quickly and confidentially, without going to court.

Learn more about asbestos trust funds →

Mesothelioma Lawsuits

If the responsible company is still in business, you may be able to file a personal injury lawsuit or a wrongful death claim.

• These cases often result in substantial settlements or jury verdicts.

• Most clients never need to go to trial—we handle the legal process on your behalf.

See how mesothelioma lawsuits work →

Veterans’ Benefits

Many veterans were exposed to asbestos during service—especially in the Navy, shipyards, or aircraft maintenance. If you served and now have mesothelioma, you may qualify for:

• Monthly compensation

• Access to specialized VA cancer treatment centers

Explore VA claims for mesothelioma →

Social Security Disability (SSDI)

Mesothelioma qualifies under the Compassionate Allowances program, which fast-tracks SSDI approval.

• You may receive monthly income and early Medicare access.

• Approval is often granted within weeks, not months.

Learn about SSDI for mesothelioma patients →

⚖️ Seeking compensation isn’t about revenge—it’s about justice, dignity, and giving your family the support they need.
If you’ve been diagnosed with mesothelioma, we can help you understand your rights and take action.

How We Can Help Your Family

A mesothelioma diagnosis affects everything—your health, your finances, your family’s future. We understand that because we’ve lived it. Our founding attorney lost multiple family members to asbestos-related cancer. That’s why we’ve built a law firm that does more than just file claims. We help families navigate the entire journey—from diagnosis to compensation to treatment.

Here’s what we offer:

Free Legal and Medical Evaluations

Not sure where to start? We’ll review your case at no cost and explain your options. We can help identify where and how you were likely exposed to asbestos—even if it happened decades ago.

Learn more about our free consultations.

Family Member Testing and Support

If one person in a household was exposed to asbestos, others may have been too. We help families understand their risk, arrange medical screenings, and secure compensation when needed.

Learn about our family health testing program.

Help Accessing Treatment

We work with top cancer centers and can help you get to the right doctors—even if they’re across the country. We’ve helped clients cover travel costs, treatment expenses, and home care through legal claims and financial aid programs.

We Handle the Paperwork—Start to Finish

You don’t need to track down old job records or medical files. We’ll do the legwork, including interviews, document retrieval, and expert review. You focus on your health—we’ll handle the rest.

💬 Call us today at 833-4-ASBESTOS or fill out the form below.
Every conversation is 100% confidential, and there’s no obligation. You’ve been through enough. Let us take care of the fight.

References:

1. 1. Strauchen, J. (2011). Rarity of malignant mesothelioma prior to the widespread commercial introduction of asbestos: the Mount Sinai autopsy experience 1883-1910. American Journal of Industrial Medicine, 54(6), 467-9.

2. 2. Enewold L, Sharon E, Thomas A. Patterns of care and survival among patients with malignant mesothelioma in the United States. Lung Cancer. 2017 Oct;112:102-108. doi: 10.1016/j.lungcan.2017.08.009. Epub 2017 Aug 10. PMID: 29191582; PMCID: PMC5726440.

3. 3. Naso, J.R., Levine, A.B., Farahani, H. et al. Deep-learning based classification distinguishes sarcomatoid malignant mesotheliomas from benign spindle cell mesothelial proliferations. Mod Pathol 34, 2028–2035 (2021). https://doi.org/10.1038/s41379-021-00850-6

4. 4. Dacic, S., Le, S. N., Husain, A., et al. (2020). Interobserver variation in the assessment of the sarcomatoid and transitional components in biphasic mesotheliomas. Modern Pathology : An Official Journal of the United States and Canadian Academy of Pathology, Inc, 33(2), 255-262.

5. 5. Brodeur, P. (1968, October 12). The magic mineral. The New Yorker, 117–165.

6. 6. Wagner, J. C., Sleggs, C. A., & Marchand, P. (1960). Diffuse pleural mesothelioma and asbestos exposure in the North Western Cape Province. British Journal of Industrial Medicine, 17(4), 260–271. https://doi.org/10.1136/oem.17.4.260

7. 7. Strickler, H. D., Goedert, J. J., Devesa, S. S., Graubard, B. I., Lahey, J., Fraumeni, J. F., & Rabkin, C. S. (1998). Trends in U.S. pleural mesothelioma incidence rates following simian virus 40 contamination of early poliovirus vaccines. Journal of the National Cancer Institute, 90(19), 1458–1461.
   https://doi.org/10.1093/jnci/90.19.1458

8. 8. Butel, J. S. (2000). Viral carcinogenesis: revelation of molecular mechanisms and etiology of human disease. Carcinogenesis, 21(3), 405–426.
   https://doi.org/10.1093/carcin/21.3.405