Malignant pleural mesothelioma is cancer that develops in the pleura, the thin tissue lining the lungs. Pleural mesothelioma is caused by exposure to asbestos. Mesothelioma of the pleura accounts for nearly 75% of all diagnoses. Symptoms of pleural mesothelioma can include chest pain, coughing, and pleural effusion.

What Is Pleural Mesothelioma?

Malignant pleural mesothelioma (MPM) is cancer that develops in the chest cavity around the lungs. Almost 75% of diagnosed mesothelioma cases form in the pleura, making it the most common of the four types. Doctors diagnose roughly 3,000 new patients with MPM every year in the United States.

A thin tissue membrane, known as the pleura, lines the lungs and chest cavity. When asbestos fibers get lodged in the lining of the lungs, they can cause inflammation and scarring. The tumors that form in the pleura are known as pleural mesothelioma.

Pleural Mesothelioma Facts

  • Rarity: Pleural is the most common type of mesothelioma
  • Symptoms: Shortness of breath, chest pain, dry cough and fatigue
  • Life Expectancy: About 40% live at least one year

The cause of pleural mesothelioma is exposure to asbestos fibers, which a person can inhale into the lungs. It usually takes from 20 to 50 years for malignant pleural mesothelioma to develop after a person’s first exposure to asbestos. Because of this latency period, the disease usually affects people older than 75.

The average life expectancy for pleural mesothelioma is often less than 18 months, but it depends on many factors.

Although there is no cure for MPM, some patients live much longer with treatment. Combining several treatments, such as surgery, chemotherapy, and radiation therapy have helped some people live for years. Clinical trials offer access to new treatments such as immunotherapy.

What Causes Pleural Mesothelioma?

Asbestos exposure is the primary cause of malignant pleural mesothelioma. After the microscopic mineral fibers are inhaled, their sharp, pointed shape causes them to lodge in the lungs and gradually migrate into the pleural lining.

Over many years, these fibers cause irritation, chronic inflammation, and genetic changes in DNA that turn healthy pleural cells cancerous.

The pleural lining of the lungs consists of two layers:

  • The outer layer lines the entire chest cavity under the ribs
  • The inner layer covers and protects the surface of the lungs

A malignant tumor can develop on either layer and may spread to the other layer. As nodules develop on the pleural surface, they grow to form tumor masses around the affected lung. The tumors can also cause pleural fluid to accumulate in the chest cavity.

The combination of tumor mass on the lung and a collection of pleural fluid increases pressure in the chest and prevents the lung from expanding, which causes breathing difficulties.

When left untreated, malignant cells can multiply and damage nearby healthy tissues or spread through the blood and lymph system, forming new tumors on distant organs.

Symptoms of Pleural Mesothelioma

For many people, mesothelioma symptoms are not noticeable until the cancer is in a later stage. 

Symptoms can include:

  • Shortness of breath
  • Chest pain or painful breathing
  • Persistent dry or raspy cough
  • Coughing up blood
  • Difficulty swallowing
  • Pain in the lower back or rib area
  • Unexplained weight loss and fatigue
  • Swelling of the face or arms
  • Night sweats or fever
  • Lumps under the skin on the chest

Patients rarely mention weight loss and fatigue during their initial doctor visits. These symptoms may only appear if the cancer is advanced. Some patients also develop swelling of the face or arms, back pain, or nerve pain.

How Pleural Mesothelioma Is Diagnosed

The diagnostic process for pleural mesothelioma begins when a doctor evaluates the initial symptoms of the disease. Chest pain and breathing difficulty warrant a chest X-ray, revealing fluid buildup or tumors around a lung. A primary care physician refers a patient to a specialist when they require further testing.

Specialists must use advanced imaging scans and tissue biopsies to confirm a pleural mesothelioma diagnosis. In addition to identifying cancer, determining the cancer stage and cell type is vital to creating an effective treatment plan.

Most cases of malignant mesothelioma are diagnosed with a high number of epithelial cells, called epithelioid type. The least common cell type is sarcomatoid mesothelioma. It is aggressive and challenging to treat, and most of these cases occur in pleural patients. The biphasic cell type is a blend of these two cell types.

Several pleural cancer symptoms and conditions may indicate a person’s history of asbestos exposure and the potential of a mesothelioma diagnosis, including pleural plaques, pleural effusions, and pleural thickening.

In a 2020 study published in Case Reports, researchers discovered a case of pleural mesothelioma through testing of metastatic gastric and colonic polyps identified in imaging scans. These polyps were the only sign that the patient had pleural mesothelioma.

Pleural Plaques

Small areas of thickening on the pleura are the most common sign someone has a prior history of asbestos exposure. Pleural plaques are not cancerous and usually do not cause symptoms, but they may indicate an elevated risk for cancer.

Pleural Effusion

Irritation from asbestos fibers can cause excess fluid to build up between the two layers of the pleura. This condition, called pleural effusion, is present in many pleural mesothelioma cases. A little fluid between the pleural layers is healthy. Too much puts pressure on the lungs, causing chest pain that worsens when you cough or take deep breaths.

Pleural Thickening

When large areas of the pleura stiffen because of scarring, it may become difficult and painful to breathe. Pleural thickening around both lungs is often a sign of significant asbestos exposure. Repeated episodes of pleural effusion can cause the pleural thickening to worsen as scar tissue collects.