Current perspective on the diagnosis of malignant pleural effusion

Malignant pleural effusion (MPE) is diagnosed by the presence of malignant cells in the pleural fluid or a pleural biopsy. The presence of MPE is classified as M1a in the 8th edition of the tumor-node-metastasis staging for lung cancer (1). Therefore, the diagnosis of MPE is important for disease staging and establishing a treatment plan in lung cancer patients. Thoracentesis is the first step in diagnosing MPE; however, its reported sensitivity varies from 40% to 87% (2,3). A pleural biopsy may be necessary in cases where the pleural fluid cytology shows a negative or indeterminate result. When pleural thickening or nodularity are noted on contrast-enhanced computed tomography (CT) images, an image-guided percutaneous pleural biopsy is recommended as the standard diagnostic method (4,5). However, these disease-related abnormalities on the pleura are not always observed on chest CT scans, and the pleural biopsy can result in false negatives.