CEACAM5 and Pleural effusion: The positive rates of CEA, CA125 and SP70 antigen in pleural effusion were higher in the malignant group than in the benign group (p>0.05); The positive rates of CEA and CA125 in the malignant group were higher than those in the benign group (p>0.05), with no statistically significant difference between the two groups in the positive rates of SP70 antigen (p>0.05).