An Overview of Malignant Pleural Effusion

Show Article Table of Contents

krisanapong detraphiphat/Getty Images

A malignant pleural effusion is a complication that involves the build-up of fluid containing cancer cells between the membranes that line the lungs. It occurs in around 30 percent of lung cancers, but can also occur with other cancers, such as breast cancer, ovarian cancer, leukemias, and lymphomas. With lung cancer, a malignant pleural effusion may be the first sign of cancer, or it can occur as a late complication of advanced lung cancer. What do you need to know about the symptoms, causes, and treatments of these effusions?


A pleural effusion is defined as an abnormal amount of fluid in the space between the layers of tissue (the pleura) that line the lungs. If cancer cells are present in this fluid (the pleural cavity), it is called a malignant (cancerous) pleural effusion. A malignant pleural effusion may be large and diffuse or small and involve just a small portion of the pleural cavity. The effusion may be all in one area, or there may be several areas of effusion (septated pleural effusions).


Almost any type of cancer can cause a pleural effusion if it is present in or spreads (metastasizes) to the chest area. The most common are breast cancer, lung cancer, ovarian cancer, and some types of leukemias and lymphomas. A pleural effusion may also be caused by the treatments for lung cancer, such as surgery, radiation therapy, or chemotherapy.


The symptoms of a malignant pleural effusion can be very uncomfortable. Shortness of breath is by far the most common symptom, occurring in around 80 percent of people. A cough may be present, and this is often positional, meaning it may be worse in certain positions such as with leaning forward or lying on one side. Chest pressure or some type of abnormal chest sensation may also occur. 


It is important to make an accurate diagnosis of a malignant pleural effusion since the prognosis and treatment are much different than for non-malignant (benign) pleural effusions. It's important to note that even with cancer, up to 50 percent of pleural effusions are benign.

A malignant pleural effusion is often first suspected because of symptoms or findings seen on a chest X-ray or CT scan. If your doctor suspects a malignant pleural effusion, the next step is usually a ​thoracentesis, a procedure in which a needle is inserted through the chest wall into the pleural space to get a sample of the fluid. This fluid is then examined under a microscope to see if cancer cells are present.

If a thoracentesis cannot be done, or if the results are inconclusive, further procedures may need to be done to get an accurate diagnosis. In some cases, a thoracoscopy (a procedure in which a thoracoscope is inserted into the chest) may need to be done to obtain a biopsy to diagnose a malignant pleural effusion.


The goal in treating a malignant pleural effusion is most often palliative, that is, to improve quality of life and reduce symptoms but not to cure the cancer. If the effusion is very small, it can sometimes be left alone. 


As noted above, thoracentesis is usually the first step used, both to diagnose the effusion (determine if cancer cells are present in the fluid and more), and to remove the fluid. Unfortunately, these effusions frequently return.

For malignant pleural effusions which recur, there are several options for treating the fluid and relieving shortness of breath. At this time there is still significant controversy over which procedure is best, and the choice is often made based on the severity of symptoms, how the tumor is responding to treatment, and your performance status—a  of how much the cancer is interfering with your ability to carry on normal daily activities.


One procedure that works in roughly 60 to 90 percent of people is called a pleurodesis. In this procedure, a tube is inserted into the pleural space and a substance, most commonly talc, is inserted between the 2 membranes lining the lungs. This chemical causes inflammation in the pleural cavity which in turn causes the 2 linings to stick together (fuse) preventing fluid from again accumulating in the pleural space. 

Indwelling Pleural Catheters

Another procedure is an indwelling pleural catheter, also known as a tunneled pleural catheter.  In this procedure, a small tube is inserted into the pleural space and tunneled beneath the skin, with a small opening on your side which can be covered with a bandage. This allows patients to drain their own fluid (with the help of a loved one) by attaching a vacuum container to the opening in the skin. A tunneled catheter is sometimes more effective if the effusion is present on both sides of the chest (bilateral) or if there are large areas of localized fluid collections (loculated effusions.) This procedure is often considered less invasive than a pleurodesis and is effective in 80 percent to 100 percent of people. Many researchers now feel that indwelling pleural catheters (IPCs) should be considered ​first line in all people with a malignant effusion.​​

There has been debate over whether pleurodesis (talc insertion) or an indwelling pleural catheter are the better option for people with advanced cancer and a recurrent pleural effusion. A 2017 study published in JAMA, sought to answer this question. The researchers found that those who had indwelling pleural catheters had fewer hospitalizations than those who had pleurodesis, primarily related to the need for procedures to remove pleural fluid. Otherwise, there were no significant differences in either the sensation of shortness of breath or the quality of life of participants.

Additional Treatment Options

If a malignant pleural effusion persists despite these other techniques, surgery may be done to drain the fluid into the abdomen, or a pleurectomy (a procedure that removes part of the pleura) may be performed. New treatments (such as medical pleuroscopy) are emerging to treat malignant pleural effusions as well. Chemotherapy may help with malignant pleural effusions due to small cell lung cancer, but is not usually very effective for with those with non-small cell lung cancer.

Choosing the Best Treatment

Before a pleurodesis or tunneled pleural catheter is recommended, a few things are necessary. First, your doctor will want to confirm that you have a malignant pleural effusion and that your symptoms are not due to another cause. Secondly, you should have a pleural effusion that recurs (comes back) after a thoracentesis. And most importantly, the draining of the fluid from your pleural space should help with your symptoms of shortness of breath. It is not necessary to remove fluid just because it is there, but only if it is causing problems (such as shortness of breath). This is a very important point to reiterate. If your shortness of breath is due to another underlying cause, and removing the fluid will not make a significant difference, there is usually no benefit in removing the fluid.


Sadly, the average life expectancy for lung cancer with a malignant pleural effusion is less than 6 months. The median survival time (the time at which 50 percent of people have died and 50 percent are still living) is 4 months, though some people have survived much longer. The prognosis is slightly better for those who have malignant pleural effusions related to breast cancer or especially ovarian cancer. With the advent of newer treatments such as targeted therapies and immunotherapy, it is hoped that these numbers will change in the near future. There are also many clinical trials in progress looking at the optimal treatment for these effusions.


The discomfort from a malignant pleural effusion can be considerable. Pair that with learning of your diagnosis and its poor prognosis, and the experience can be distressing for anyone—particularly those who already have a malignant pleural effusion when they are first diagnosed with cancer. Ask questions. Ask for help from others, and allow them to give it. Talk to your doctor about managing pain from lung cancer. Consider joining a support group. Your emotions may span the spectrum from anger to disbelief, to depression. That is normal. Seek out friends and loved ones who are willing to truly listen and support you. Learn more about stage 4 (metastatic) lung cancer.  

For Loved Ones

Very few people experience lung cancer in isolation, and for loved ones the disease can feel as overwhelming and frightening and added to that is a heartwrenching sense of helplessness. What should you know when your loved one has cancer?

Was this page helpful?
Article Sources