What Is Malignant Pleural Effusion?

A malignant pleural effusion is a buildup of fluid in the pleural tissue of the lungs and chest cavity that has occurred secondary to a cancerous process. Often breast cancers, lymphomas, and lung cancers can cause this fluid buildup to occur. Symptoms caused by a malignant pleural effusion can include shortness of breath and chest pain on deep inspiration. Diagnosis relies on physical exam findings, radiographic characteristics, and analysis of fluid removed from the pleural cavity. Treatment can include removing the excess pleural fluid or treating the underlying cancer.

The surface of the lung is encased by a lining called the pleura, and the space between the lung and this membrane is called the pleural cavity. Normally this space is only filled with a very small amount of fluid. In a number of pathologic processes, however, this space can fill with fluid, and a condition called a pleural effusion develops. Diseases such as congestive heart failure, pneumonia, or other infections can cause these effusions to occur. Sometimes a cancerous process can cause the effusion to occur, and when this happens the condition is called a malignant pleural effusion.

Certain cancers are known to be causes of malignant pleural effusions. They are most commonly associated with lung cancers, lymphomas, and cancers of the breast. Other cancers could also cause these fluid accumulations to occur, but they are much less common causes of this finding.

A malignant pleural effusion can be diagnosed on the basis of a number of different symptoms, physical exam findings, radiographic results, and analysis of the pleural fluid itself. Symptoms can include shortness of breath and a stabbing chest pain that occurs with deep inspiration. On physical exam, this condition can be identified by tapping, or percussing, the lung fields and determining whether fluid is present in an abnormal location. Radiographic studies including x-ray and chest computed tomography (CT) imaging can identify the fluid accumulation.

Definite diagnosis of a malignant pleural effusion relies on taking a sample of the pleural fluid and analyzing it. This fluid is typically obtained by performing a thoracentesis, which is procedure where a health care provider inserts a needle between the ribs and uses it to aspirate the pleural fluid. The aspirated fluid is analyzed to determine the concentration of species such as glucose, protein, white blood cells, and red blood cells. When a malignant pleural effusion is suspected, the fluid is also sent for cytology analysis, which is a technique used to identify the presence of malignant cells.

The treatment of a malignant pleural effusion can employ a number of different techniques. In some cases, treating the underlying cancer could alleviate the effusion. Often the thoracentesis process itself can alleviate some of the symptoms caused by the effusion, because removing the fluid relieves some of the pressure on the lung and decreases the shortness of breath felt by the patient. Sometimes during the aspiration process an irritating agent is injected into the pleural cavity, which allows the surface of the lung to adhere to the pleura, preventing further accumulation of fluid.