Soluble receptor-binding cancer antigen expressed on SiSo cells in pleural fluid - A potential diagnostic marker for malignant pleural effusion

Background: We sought a marker to differentiate malignant from nonmalignant pleural effusions. Methods: We studied 41 patients presenting with pleural effusions to the National Sanyo Hospital between April 2000 and January 2002 (33 men and 8 women; mean age, 68 years). Twenty patients (49%) were proven to have malignant pleural effusions, while 21 patients (51%) had nonmalignant pleural effusions. Thoracentesis was performed. Results: The mean (+/- SD) concentration of receptor-binding cancer antigen expressed on SiSo cells (RCAS1) in malignant pleural effusions, measured by enzyme-linked immunosorbent assay, was significantly higher than that in nonmalignant pleural effusions (15.1 +/- 33.6 vs 1.4 +/- 0.81 U/mL, respectively; p < 0.05). Conclusion: The determination of the RCAS1 concentration in pleural fluid is informative in the diagnosis of malignant pleural effusions.