Pleural and serum markers for diagnosis of malignant pleural effusion

Differentiation between benign and malignant exudative pleural effusion remains a clinical challenge. Recently, several markers have been reported to increase the diagnostic accuracy of malignant pleural effusion, with controversial results.

Patients with exudative pleural effusion were divided into 2 groups: a malignant pleural effusion group (39 patients) diagnosed by malignant cells in pleural fluid cytology or by malignant infiltration of the pleura on pleural biopsy, and a benign pleural effusion group (51 patients) with neither malignant cells in pleural fluid cytology nor malignant infiltration of the pleura on pleural biopsy. Matrix metalloproteinase-9 and tissue inhibitor of metalloproteinase-1 were determined in both serum and pleural fluid samples, using commercially available enzyme-linked immunosorbent assay kits.

The etiology of malignant pleural effusion in the malignant group was breast cancer in 43.6% and bronchogenic carcinoma in 25.6%. There was a statistically significant difference between the 2 groups regarding sex, with more males in the benign group. There was no significant difference between groups regarding age. The median levels of matrix metalloproteinase-9 and tissue inhibitor of metalloproteinase-1 were higher in the malignant group than in the benign group, and the differences were highly significant in both pleural fluid (p < 0.001) and serum (p < 0.001).

Matrix metaloproteinase-9 and tissue inhibitor of metalloproteinase-1 in serum and pleural fluid samples might be valuable markers for differentiating benign from malignant pleural effusions.