Synopsis
Diagnose malignant pleural effusion efficiently and choose symptom-led definitive drainage that respects lung expandability, prognosis, cancer treatment, home support and patient preference.
- A malignant pleural effusion usually indicates advanced cancer but prognosis and treatment options vary greatly by tumour type, molecular target, performance status and response to systemic therapy.
- Breathlessness is the main treatment indication. Effusion size alone does not prove that fluid is the cause, especially with embolism, lymphangitic disease, airway obstruction or cardiac comorbidity.
- Use thoracic ultrasound for every fluid procedure and obtain contrast-enhanced staging CT at the appropriate point in the diagnostic pathway.
- Pleural-fluid cytology is a first diagnostic test for many suspected malignancies, but sensitivity varies; negative cytology does not exclude pleural cancer, particularly mesothelioma.
- Plan specimen volume, cell block, immunocytochemistry and molecular requirements with pathology rather than repeatedly sending low-value small samples.
- A therapeutic aspiration can show whether breathlessness improves and whether the lung expands, helping choose definitive treatment.
- For recurrent symptomatic effusion with expandable lung, offer a choice between indwelling pleural catheter and talc pleurodesis, explaining hospital time, home drainage, recurrence and adverse effects.
- An indwelling pleural catheter is usually preferred when lung is non-expandable or pleurodesis has failed; drainage frequency can be tailored to symptom control or a goal of autopleurodesis.
- Do not defer definitive pleural control solely to wait for systemic anticancer treatment when the patient remains symptomatic.
- Early palliative-care involvement complements active oncology by addressing breathlessness, anxiety, function and advance care needs.
Key red flags
Severe distress, hypoxaemia, hypotension or major mediastinal displacement from a large effusion requires urgent monitored drainage and simultaneous assessment for other causes.
Fever, pleuritic pain, neutrophilic fluid, low pH, purulence or an infected catheter requires prompt antibiotics and pleural-team review rather than attribution to malignancy alone.
Sudden pleuritic pain, haemoptysis, stridor, unilateral leg swelling or neurological deficit may indicate pulmonary embolism, central-airway obstruction or metastatic complication rather than fluid burden.
Investigation priorities
Confirm fluid, septation, pleural abnormality and a safe intervention site.
Management branches
A new unilateral effusion is suspicious for malignancy.
- Use thoracic ultrasound and contrast-enhanced CT to define fluid, pleural targets, primary cancer and alternative causes.
- Perform image-guided aspiration when safe, sending an adequate cytology and cell-block sample plus tests for competing infection or transudative disease.
- If cytology is nondiagnostic and suspicion remains, move to image-guided biopsy or thoracoscopy rather than serial low-yield aspirations.
- Coordinate respiratory, pathology, radiology and oncology plans so tissue meets histological and molecular treatment needs.