Abstract: Objective　To investigate the relationship between the detection results of exfoliative cytology and tumor markers when serous membranes were encroached by malignant tumor cells.   Methods　An analysis was performed on the results of exfoliative cytology examination and tumor marker levels in serum and serous membrane cavity effusion among 158 patients with definite history of malignant tumors. The patients were classified into 2 groups according to the positive or negtive detection of tumor cells.  Results　Carcinoembryonic antigen (CEA), carbohydrate antigen 199 (  CA199) and carbohydrate antigen 125 (CA125) levels were significantly higher in serous membrane cavity effusion ［  294.85(6.031 000.00)μg/L, 367.00(8.821 000.00) kU/L and 3 435.00(922.20~5 000.00) kU/L］ than those in sera ［9.98(0.481 000.00)μg/L, 23.76(0.661 000.00) kU/L and   90.55(47.211 796.00) kU/L］ in patients with malignant tumor cell group (P<0.05). There was no statistical significance in patients without malignant tumor cell group ［1.67(0.20373.08)μg/L, 13.13(4.34725.10) kU/L and 11.23(6.83172.50) kU/L in serous membrane cavity effusion; 2.69(0.20110.90) μg/L, 31.22(6.701 000.00) kU/L and 19.32(17.20491.10) kU/L in sera, P>0.05］. A statistical significance of CEA, CA199 and CA125 levels were further disclosed between the patients with and without malignant tumor cells in their serous membrane cavity effusions (P<0.01). As concern to the classification of nucleated cells in patients with malignant tumor cell group, the patients with >50% lymphocytes accounted for 61.4% (70/114), while the patients with >25% macrophages accounted for 42.1% (48/114). Conclusions　The infiltration of malignant tumor cells on serous membrane cavity membrane induces the increasing levels of tumor markers and aggregation of lymphocytes and macrophages in the serous membrane cavity effusion. 

Key words: Serous membrane cavity effusion, Exfoliative cytology, Tumor marker