Lung cancer fluid in the lungs is an accumulation of fluid that accumulates in the chest and is termed a pleural effusion. The presence of pleural effusion with lung cancer is said to be the advanced stage of the condition. Two sheets of tissues protect the lungs, which are called pleural membranes. In between these, the pleura is the pleural space, and thin layers of fluid are expected to be present in this space as it helps the lungs move quickly while inhaling and exhaling.
https://drarvindkumar.com/blog/pulmonary-edema.php