Malignant pleural effusion is defined by which finding?

Malignant pleural effusion is defined by which finding?

• A. Malignant cells in the pleural fluid
• B. Elevated protein
• C. Increased LDH
• D. Bacterial infection

Answer: (A)

The defining finding for malignant pleural effusion is the presence of malignant cells in the pleural fluid (or in pleural tissue). Detecting cancer cells in the fluid confirms that the malignant process involves the pleural space, which sets this effusion apart from other causes. Elevated protein or LDH levels indicate an exudate in general but do not by themselves prove malignancy, and a bacterial infection points to an infectious cause rather than cancer. In practice, pleural fluid cytology or pleural biopsy showing malignant cells is what confirms malignant pleural effusion.

The defining finding for malignant pleural effusion is the presence of malignant cells in the pleural fluid (or in pleural tissue). Detecting cancer cells in the fluid confirms that the malignant process involves the pleural space, which sets this effusion apart from other causes. Elevated protein or LDH levels indicate an exudate in general but do not by themselves prove malignancy, and a bacterial infection points to an infectious cause rather than cancer. In practice, pleural fluid cytology or pleural biopsy showing malignant cells is what confirms malignant pleural effusion.