Mesothelium

What Is the Mesothelium?

The mesothelium is a thin membrane made of specialized cells called mesothelial cells. This membrane protects organs and is where mesothelioma, a cancer affecting this tissue, develops. It helps your body react to injuries and diseases. 

The mesothelium moves serosal fluid, a slippery liquid that lowers friction, across body cavities. It also controls inflammation, which is your body’s response to injury or infection. Doctors name these membranes based on the organs they cover.

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Locations of the Mesothelium

• Pericardial mesothelium: Covers your heart
• Peritoneal mesothelium: Covers organs in your belly and your abdominal wall
• Pleural mesothelium: Covers your lungs and chest wall.
• Tunica vaginalis: Covers the testes

When you inhale asbestos fibers, they can stick in the mesothelium. These fibers irritate and damage soft tissue over time. The lymphatic system, which removes waste and fights infections, carries asbestos fibers deeper into mesothelial layers. Asbestos causes malignant mesothelioma, lung cancer, asbestosis (lung scarring) and other diseases.

Mesothelium Structure and Function

The mesothelium has 2 layers: visceral and parietal. The visceral mesothelium covers your internal organs. The parietal mesothelium covers your serosal cavity, which is the space around those organs where serosal fluid moves. 

Serosal fluid contains proteins and cells that help repair tissue or respond to inflammation, supporting the mesothelium’s protective role. Although the mesothelium protects your body, its tissue renews slowly. Less than 1% of mesothelial cells divide at any time.

Functions of the Mesothelium

• Blood clotting to heal wounds
• Inflammation and tissue repair
• Presenting immune proteins to lymphocytes, which are immune cells
• Protecting against invading microorganisms
• Transporting fluids and cells
• Tumor cell adhesion to help prevent cancer from spreading

Research on immune cells and mesothelial cells has improved over the last decade. Studies on immunotherapy, a treatment that helps the immune system fight cancer, show how immune cells and mesothelial cells  interact. This research may improve treatment for people with mesothelioma cancer.

Diseases of the Mesothelium

Cancers like mesothelioma can start in the mesothelium from inflammation and scarring. If this damage doesn’t heal, the mesothelium may develop fibrous adhesions, which are bands of scar tissue that cause tissues or organs to stick together abnormally. These changes can lead to complications.

Benign conditions also develop in the mesothelium. For example, mesothelial hyperplasia is a non-cancerous condition where mesothelial cells multiply more than usual. This often happens in response to injury or inflammation. While benign, it may look like cancer under a microscope. 

Effusions, also benign, are fluid buildups between layers of the mesothelium. A pleural effusion collects around your lungs. A peritoneal effusion, also called ascites, collects around your abdomen. Pericardial effusions can happen around the heart. Hydroceles, which are testicular effusions, also occur.

Survivor Jayda K. tells us a peritoneal effusion aided her mesothelioma diagnosis. She explains, “As a young woman with abdominal pain, I had a really hard time convincing someone I was in pain. A really hard time. I was told it was just my period.” Doctors removed more than a gallon of fluid and saw tumors on her peritoneum. A biopsy confirmed her peritoneal mesothelioma diagnosis.

Pleural Diseases

Pleural mesothelioma is the most serious disease of the pleura. It, along with other benign and cancerous conditions, can develop from asbestos exposure. These diseases affect the membrane surrounding your lungs and can cause a range of breathing problems.

Types of Pleural Diseases

• Atelectasis: Contracts pleural scar tissue and folds the pleura into the lung, causing the lungs to underinflate
• Pleural mesothelioma: Cancer of the pleura
• Pleural plaques: Fibrous scar tissue on the pleura that may become calcified
• Pleural thickening: Involves extensive scarring that thickens and restricts the pleura
• Pleuritis: Inflammation of the pleura

The latency period for pleural mesothelioma is between 20 and 60 years. Other pleural diseases linked to asbestos exposure also have long latency periods before symptoms appear or a diagnosis is made. If you notice symptoms or develop pleural diseases, it’s important to see a doctor early. An earlier diagnosis can improve treatment outcomes.

Peritoneal Diseases

The peritoneum can develop both benign and cancerous diseases including peritoneal mesothelioma. Other conditions can affect the peritoneum such as scar tissue formation, inflammation and fluid buildup. Some of these peritoneal diseases have causes distinct from mesothelioma.

Types of Peritoneal Diseases

• Intra-abdominal adhesions: Scar tissue bands that form wounds in the peritoneum
• Peritoneal mesothelioma: Rare, aggressive cancer of the peritoneum
• Peritonitis: Inflammation of the peritoneum often from bacterial or fungal infection
• Primary peritoneal serous carcinoma: Another cancer of the peritoneum
• Ultrafiltration failure: Condition where the peritoneum can’t properly filter, leading to fluid buildup

Primary peritoneal serous carcinoma is a rare cancer similar to advanced-stage serous ovarian carcinoma. A 2022 study published in the Scholars Journal of Medical Case Reports compared these cancers, highlighting the importance of understanding this disease. 

Symptoms may be vague early on but can include abdominal swelling, pain and fluid buildup (ascites). Because these diseases typically develop over many years, early diagnosis and care improve outcomes.

Pericardial Diseases

Several benign conditions and cancers can develop in the pericardium. Disorders in this membrane are often difficult to identify because its proximity to the heart can lead to subtle or misleading symptoms. People with pericardial diseases might notice signs that resemble other heart or systemic issues. 

Types of Pericardial Diseases

• Cardiac tamponade: Compression of the heart from fluid accumulation
• Pericardial constriction: Scarring and loss of elasticity in the pericardium
• Pericardial mesothelioma: Rare cancer of the pericardium
• Pericarditis: Inflammation of the pericardium, often linked to infection or other causes
• Other cancers: Sarcomas, lymphoma and primitive neuroectodermal tumors can also develop in the pericardium

Pericardial mesothelioma accounts for about 1% of all mesothelioma cases but can have especially severe effects. Diseases in this region may affect circulation, breathing or overall well-being and sometimes develop with few warning signs. Others may cause chest pain, swelling or changes in heart rhythm.

In addition to mesothelioma, a range of noncancerous and malignant disorders can disrupt heart function or complicate diagnosis. Inflammation, scarring and abnormal fluid accumulation are the most frequent noncancerous issues encountered in this area.

Tunica Vaginalis Diseases

Several benign and cancerous conditions can arise in the tunica vaginalis. Testicular mesothelioma is the most common asbestos-related cancer affecting this membrane. Disorders here can cause symptoms such as scrotal swelling, discomfort or unusual lumps, and may require careful clinical evaluation.

Types of Diseases of the Tunica Vaginalis

• Adenomatoid tumors: Benign tumors often found in the tunica vaginalis
• Fibrous pseudotumors: Noncancerous fibrous lesions of the tunica vaginalis
• Hydrocele: Excess fluid accumulation between the layers of the tunica vaginalis causing swelling
• Lipoma and leiomyoma: Benign tumors arising from fat or smooth muscle tissue, respectively
• Scrotal calculi: Calcified deposits forming between tunica vaginalis layers
• Testicular mesothelioma: Rare cancer originating in the tunica vaginalis
• Various malignant tumors: Other malignant tumors that can develop in the tunica vaginalis include mesenchymal malignant tumors, lymphomas and serous borderline malignant tumors

If you have a history of asbestos exposure and notice unusual symptoms involving your lungs, abdomen, heart or testes, consult your healthcare provider right away. Early evaluation is important for appropriate diagnosis and management.

Mesothelium and Asbestos Exposure

Scientists continue to study how asbestos fibers travel through the body to reach the mesothelium. A 2023 study in PNAS highlights the lymphatic system as a critical pathway. The lymphatic system is a network of tiny vessels and small structures called lymph nodes. It carries a clear fluid called lymph through your body, helping to remove waste, germs and damaged cells from tissues. This system also supports your immune system, helping fight infections and disease.

While the lymphatic system normally protects your body, some asbestos fibers can move through these vessels and settle in the mesothelium. Once lodged there, the fibers may remain for many years, causing persistent irritation and damage. This ongoing damage increases the risk of developing mesothelioma and other diseases affecting the mesothelium.

Because asbestos-related diseases develop slowly and often show vague symptoms, avoiding exposure remains the most effective way to reduce risk. Proper safety precautions are essential when handling materials that may contain asbestos, especially in older buildings or industrial settings. Anyone who suspects asbestos contact should seek medical evaluation promptly for early detection and diagnosis.

How Are Diseases of the Mesothelium Treated?

The choice of treatment doctors use depends on the specific diagnosis and the location of the affected mesothelial tissue. Cancerous conditions often require multimodal therapy, combining different methods to control tumor growth and symptoms. In contrast, benign diseases typically don’t need aggressive intervention and focus on managing symptoms.

Treatments for Diseases of the Mesothelium

• Chemotherapy: Strong medicines used to kill cancer cells
• Immunotherapy: Drugs that stimulate the immune system to shrink tumors
• Radiation therapy: Use of targeted radiation to shrink tumors and ease pain, particularly in chest wall tumors
• Surgery: Minimally invasive surgeries drain excess fluids and relieve symptoms; more aggressive surgeries remove mesothelial tumors to slow disease progression

Treatment plans are tailored to each patient’s overall health and the particular type of mesothelial disease involved. With appropriate care, doctors help patients manage their conditions and improve quality of life.

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