To compare pleural effusion cytology, pleural biopsy, the coagulum of pleural effusion with their positive diagnostic rates of malignant pleural effusion;

• 目的：比较胸腔积液(胸液)细胞学、胸膜活检、胸液块状凝集物(凝集块)3种病理标本的获取方法及对恶性胸液的诊断阳性率；