Lung cancer with pleural effusion is not necessarily advanced, because the nature of pleural effusion is still uncertain. There are some pleural effusion caused by inflammation, which is also possible in early or middle stage lung cancer, and further symptomatic treatment such as anti-inflammatory, asthma, cough suppression and sputum removal is needed. If there is more pleural fluid, thoracentesis and fluid extraction are needed. The primary lesion of lung cancer also needs to be treated by applying surgery or radiotherapy, chemotherapy, targeted, immunotherapy, etc. If pleural effusion is done for thoracentesis aspiration and all that comes out is bloody pleural fluid, the possibility of advanced stage is higher. When chest fluid tests are done, often cancer cells may be found inside the pleural fluid, which is called malignant pleural effusion. Generally, the treatment effect is not good, but you can also consider doing chest perfusion chemotherapy to relieve symptoms and prolong survival.