I. Characteristics of malignant pleural effusion: often non-specific in appearance, may be bloody, yellowish or buttermilk-like, often exudate, high protein (>30 g/L), high lactate dehydrogenase (>200 U), high CEA (>200 g/L), high amylase (>160 U), low PH (<7.3), low glucose (<600 g/L), possible detection in pleural fluid of cancer cells. Clinical manifestations of malignant pleural effusion: 1. dyspnea: shortness of breath or dyspnea when moving, or even unable to lie down and need semi-recumbent position. 2. 2. Chest pain: Tumor involves wall pleura, intercostal nerve, ribs or other structures, which may cause chest pain, with different degrees of pain, such as vague pain, swelling pain or severe pain, radiating to upper abdomen and shoulder. 3, wasting and chronic disease appearance. 4.Supraclavicular lymph node enlargement. Diagnostic methods of malignant pleural effusion: 1, thoracentesis aspiration cytology, positive rate of 66%. 2, closed drainage of the chest cavity to obtain pleural fluid for examination. 3.Pleural puncture biopsy, positive rate 46%. 4.TV thoracoscopy 95% can confirm the diagnosis and get treatment at the same time. Through the above methods to take pleural fluid for cytological examination, take pleural table for histological examination.