1: What is a Malignant Pleural Effusion?

Where exactly is this fluid?

The fluid is outside of the lung itself, in between the lung and the ribcage. The outside of the lung is covered by a very thin outer lining like a layer of clingfilm. There is another thin lining on the inside of the rib cage. Normally the lung is pressed up against the inside of the ribcage and the two clingfilm linings touch each other. There is a very tiny amount of fluid between these two linings. These linings are called the ‘pleura’ and the fluid between the two linings is called ‘pleural fluid’.

Why does cancer cause a pleural effusion?

Cancer can affect the pleura in two ways; a cancer that starts in the pleura or a cancer from somewhere else in the body that spreads to the pleura. When cancer affects the pleura it causes more fluid to be squeezed out of the tiny blood vessels, like opening a tap so more water comes out. The cancer also blocks the holes that drain the fluid away, like putting a plug in the bath with the tap running.

How much fluid could there be?

It is surprising how much fluid can build up in the chest and can often reach a few litres!

What are the symptoms of a malignant pleural effusion?

The main symptom is difficulty in breathing. This may only be noticeable when a person exercises at first but this could get more noticeable as the amount of fluid gets worse. Some people with a malignant pleural effusion may notice breathing difficulties when lying down on their back or lying on one side.