A 62-year-old woman with a history of smoking presents with a 2-month history of progressive dyspnoea and chest pain. Chest X-ray shows a 5 cm mass in the right hilum with ipsilateral pleural effusion. Thoracentesis fluid is exudative with negative cytology for malignant cells on first sampling. Which investigation is most appropriate to establish the diagnosis of lung cancer and assess pleural involvement?

Explanation

## Investigation of Choice for Hilar Mass with Pleural Effusion ### Clinical Context A hilar lung mass with pleural effusion raises concern for advanced non-small cell lung cancer (NSCLC) with pleural involvement. The negative initial thoracentesis cytology does not exclude malignancy; pleural cytology sensitivity is only 40–60% on first tap and improves to ~80% with repeat sampling or alternative techniques. However, the primary goal here is to establish tissue diagnosis of the lung mass itself and assess mediastinal lymph node involvement. ### Why EBUS-TBNA is Optimal **Key Point:** EBUS-TBNA is the gold standard for sampling hilar and mediastinal lymph nodes and is superior to transbronchial biopsy for central masses. It provides both diagnosis and staging in a single procedure [cite:Harrison 21e Ch 87]. 1. **Direct Lymph Node Access**: EBUS allows real-time ultrasound visualization of hilar (station 10L/R) and mediastinal lymph nodes (stations 2–9), enabling precise needle placement. 2. **High Diagnostic Yield**: Sensitivity 85–95% for malignancy in enlarged lymph nodes; superior to blind transbronchial biopsy (50–70%). 3. **Staging Information**: Simultaneous assessment of N-stage (mediastinal involvement) guides treatment decisions (surgery vs. chemoradiotherapy). 4. **Pleural Involvement Assessment**: Biopsies of involved lymph nodes and adjacent tissue help determine resectability and stage. 5. **Minimally Invasive**: Performed via flexible bronchoscope; no general anaesthesia required; low morbidity. ### Comparison of Diagnostic Approaches | Investigation | Target | Yield for Hilar Mass | Staging Capability | Invasiveness | |---|---|---|---|---| | **EBUS-TBNA** | Hilar/mediastinal nodes | 85–95% | Excellent (N-staging) | Bronchoscopic, low risk | | **Repeat thoracentesis** | Pleural fluid | 40–80% (depends on volume, technique) | None for lung mass | Low risk but limited diagnostic value | | **Transoesophageal EUS** | Posterior mediastinal nodes (stations 5, 8, 9) | 80–90% for posterior nodes | Partial (limited to posterior stations) | Endoscopic, moderate risk | | **Mediastinoscopy** | Anterior/middle mediastinal nodes (stations 2, 3, 4) | 90–95% | Excellent but invasive | Surgical, general anaesthesia, higher morbidity | **Clinical Pearl:** EBUS-TBNA has largely replaced mediastinoscopy as the first-line invasive staging tool for suspected NSCLC because it is less invasive, has comparable diagnostic yield, and can be combined with transbronchial biopsy of the primary mass if accessible. ### Diagnostic Algorithm for Hilar Mass ```mermaid flowchart TD A[Hilar Mass on CXR/CT]:::outcome --> B{Endobronchial involvement?}:::decision B -->|Yes, visible at bronchoscopy| C[Transbronchial Biopsy]:::action B -->|No, or mass not visible| D[EBUS-TBNA of hilar/mediastinal nodes]:::action C --> E[Tissue Diagnosis + EBUS for N-staging]:::action D --> F[Tissue Diagnosis + N-staging]:::outcome F --> G{Pleural Effusion Present?}:::decision G -->|Yes, cytology negative| H[Consider Pleural Biopsy or Pleuroscopy if diagnosis unclear]:::action G -->|No| I[Proceed to Full Staging: PET-CT, Brain MRI]:::action H --> I I --> J[Treatment Planning]:::outcome ``` **High-Yield:** EBUS-TBNA is the preferred first-line invasive investigation for hilar/mediastinal masses because it provides both diagnosis and staging with minimal morbidity. Mediastinoscopy is reserved for cases where EBUS is non-diagnostic or when anterior mediastinal nodes need biopsy.