Cytology via thoracentesis remains the first-line approach for diagnosing malignant pleural effusion (MPE), yet its sensitivity is limited. leaving many patients undiagnosed or delayed in treatment. In this expert-led discussion, Dr. David Feller-Kopman explores the limitations of current diagnostic methods and the evolving role of biomarkers in enhancing both diagnostic accuracy and prognostic insight. Dr. Feller-Kopman is a Professor of Medicine at the Geisel School of Medicine at Dartmouth and the Chief of Pulmonary and Critical Care Medicine at Dartmouth-Hitchcock Medical Center, and he discussed this topic at the 2025 CHEST Annual Meeting.