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Pleural Effusion

When fluid collects in the lining between the lungs and chest cavity, it is termed pleural effusion. Pleural effusion is a symptom of a greater disease. For mesothelioma patients, effusion is common and can affect the pleura or pericardium.

Effusions of the pleural cavity can be either exudative or transudative, based on microscopic and chemical analysis of the fluid. Exudative pleural effusion is caused by inflammation of the lung from a tumor growth, which is most common in patients with mesothelioma. Transudative pleural effusions occur when fluid leaks into the pleural cavity and have been identified in a few pleural mesothelioma cases. In general, pleural effusions are quite common in mesothelioma cases, as well as due to other conditions. According to the National Cancer Institute, there are about 100,000 pleural effusions diagnosed each year in the United States.

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What Is Pleural Effusion?

A pleural effusion is a buildup of excess fluid within the chest cavity. If left untreated and allowed to accumulate, the fluid may prevent the lungs from fully expanding and inhibit breathing. The cause of the effusion may be related to cancer, cancer treatments like radiation and chemotherapy or various other medical conditions. Malignant effusions are commonly caused by leukemia, lymphoma or cancers of the breast and lung, including pleural mesothelioma. As many as 50% of all metastatic cancer patients will develop pleural effusions. Between 80 – 95% of malignant pleural mesothelioma patients have pleural effusions when diagnosed.

Diagnosing Symptoms of Pleural Effusion

A pleural effusion is a sign of a larger disease, but the condition itself has accompanying symptoms that can alert patients and their healthcare teams that there may be a fluid buildup. The most common symptom associated with a pleural effusion is dyspnea or breathlessness, with about 30% of pleural mesothelioma patients experiencing breathlessness caused by a pleural effusion.

For some patients, effusions may be asymptomatic or can present with unrelated symptoms stemming from the underlying condition. For pleural mesothelioma patients, the most common symptoms include weight loss and fever, which can be easily confused for more common illnesses.

Symptoms of Pleural Effusion
  • Breathlessness (dyspnea)
  • Dry cough
  • Dull chest pain
  • Wheezing

After a patient presents with symptoms, analysis of a pleural fluid sample is often the first step in the diagnostic process to identify if the buildup is malignant or benign and help determine the cause. The presence of proteins in the pleural fluid can signal to a patient's healthcare team if the effusion is exudative or transudative, since exudative effusions tend to have more proteins present than transudative effusions.

Doctors may also be able to differentiate the types of effusions by the presence of pleural thickening. Typically, malignant effusions are accompanied by the thickening of the lung linings, and exudative effusions are often malignant, while transudative effusions may be benign. Since malignant effusions tend to recur, patients may also experience worsening pleural thickening over time as more scar tissue builds.

To definitively diagnose a patient with either malignant or benign effusion, the fluid testing is commonly followed by a tissue biopsy. Imaging tests, such as a chest X-ray, MRI (magnetic resonance imaging) or CT scan (computed tomography) may also be used as diagnostic tools to help determine where a biopsy should be taken and identify any other visible health concerns, like tumors. Overall, doctors have found that about one-third of pleural fluid samples are malignant.

Prognosis of Pleural Effusion

Prognosis for patients with pleural effusions varies based on the underlying condition causing the retention of pleural fluids. Regardless of diagnosis, if pleural effusions persist or recur regularly, a patient may face a worse prognosis than those whose effusions are able to be treated without recurrence. Pleural effusions caused by liver disease, heart failure or cancers, including mesothelioma, will likely persist unless treated effectively.

Mesothelioma patients experiencing pleural effusions often have less than 10 months to live following their diagnosis, as they typically have an advanced stage of disease including metastasis into the lymph nodes. In comparison, the median survival time for patients with early stage pleural mesothelioma, without effusions, is about 20 months. However, an individual’s prognosis can vary depending on a number of factors including cell type, the patient’s age and overall health.

As mesothelioma progresses further into the late stages of disease and the tumor engulfs the pleural space, fluid buildup is inhibited and existing pleural effusions may tend to dissipate.


Symptom management is the main goal of pleural effusion treatment, though the course of treatment differs depending on the cause of the symptom. For instance, benign and transudative effusions are less likely to recur after a procedure to drain the fluid. Malignant effusions experienced by those diagnosed with pleural mesothelioma or asbestos lung cancer may not be as easy to manage and can recur frequently. For most mesothelioma patients experiencing the symptom, a palliative treatment plan will be recommended.

Pleural effusions caused by malignant mesothelioma may be treated with multimodal therapy including surgery, chemotherapy or radiation therapy. Though in most cases these treatments will be applied palliatively since pleural effusion indicates metastasis and a later stage of disease, some patients may be able to receive the treatments to improve life expectancy. Even for these patients, palliative treatments may also be used to better manage pleural effusion and other symptoms and improve quality of life.

Early detection and treatment of pleural effusions, and the underlying conditions, is crucial in order to increase survival rates. Those who are not properly diagnosed until the advanced stages of disease are often not candidates for aggressive curative treatment options and may instead receive palliative care to manage symptoms.

Those who’ve had asbestos exposure should seek medical attention if they experience symptoms of asbestos-related disease, including pleural effusions. Finding mesothelioma at an earlier stage is the best way to improve patient outcomes.

Author: Linda Molinari

Editor in Chief, Mesothelioma Cancer Alliance

Linda Molinari

Reviewer: Dr. James Stevenson

Medical Reviewer and Thoracic Medical Oncologist

Dr. James Stevenson

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