Malignant Pleural Effusion

Neoplastic pleural effusion (malignant pleural effusion): malignant cells are usually found in the pleural fluid; if effusion is accompanied by metastatic nodules on mediastinal or pleural surface, the diagnosis is made regardless of cytology.

Common Symptoms

Dyspnea; shortness of breath; fatigue; cyanosis

Causes and Pathogenesis

(1) Etiology: neoplastic effusion = 38-53% of all pleural effusions; pleural metastatic tumors and diffuse malignant mesothelioma are the main causes. (2) Mechanism: parietal pleura has 2-12nm stomata communicating with lymphatics; normal 100-200ml/day produced by parietal filtration and reabsorbed through stomata; visceral pleura contributes little. Starling forces: intrapleural pressure -0.49kPa (-5cmH2O); fluid protein 1.7%, oncotic 0.78kPa (8cmH2O); parietal capillary hydrostatic 1.078kPa (11cmH2O); pleural capillary oncotic 3.33kPa (34cmH2O); normal pleural space 5-15ml. Mechanisms of malignant effusion: (1) parietal/visceral pleural metastases damage capillaries → bloody effusion. (2) Lymphatic obstruction: tumor blocks pleural lymphatics; blockage between pleural stomata and mediastinal nodes (tumor emboli, mediastinal node metastases) impairs reabsorption. (3) Tumor-cell protein release: rapidly growing tumor cells detach, necrose, release protein → increased intrapleural oncotic pressure. (4) Increased pleural permeability: tumor implants/invasion cause inflammation; capillary leak; obstructive pneumonia from lung cancer causes parapneumonic-like effusion. (5) Lowered intrapleural pressure/higher capillary hydrostatic: bronchial obstruction → atelectasis → more negative pleural pressure (from -1.176 to -4.7kPa = ~200ml fluid); tumor invades vena cava/pericardium → venous obstruction. (6) Other: tumor emboli → pulmonary infarction; hypoalbuminemia; post-radiation exudate.

Treatment

Drug, supportive therapy

Preventive Measures

No effective prevention; early diagnosis/treatment.

Department to Visit

It is recommended to visit the Cardiothoracic Surgery department; an appointment can be booked on this platform before the visit.

Warm reminder: The above information is for health science reference only and cannot replace professional medical diagnosis. If you have related symptoms, please seek medical attention at a regular hospital promptly.