A 58-year-old male smoker presents with a 3-month history of progressive dyspnea, chest pain, and weight loss. Chest X-ray shows a central hilar mass with mediastinal widening. CT chest confirms a 4 cm central lung lesion with ipsilateral hilar and mediastinal lymphadenopathy. Bronchoscopy with endobronchial biopsy is planned. Which investigation is most appropriate to confirm the diagnosis and guide further management?

Explanation

## Investigation of Choice for Central Lung Mass with Mediastinal Involvement ### Clinical Context The patient has a central hilar mass with mediastinal lymphadenopathy — a presentation highly suggestive of small cell lung cancer (SCLC). The lesion is accessible via the airways, making bronchoscopic sampling the preferred first-line approach. ### Why EBUS-TBNA is Optimal **Key Point:** EBUS-TBNA combines bronchoscopic visualization with real-time ultrasound guidance to sample mediastinal and hilar lymph nodes with high sensitivity (90–95% for SCLC) and specificity. **High-Yield:** EBUS-TBNA is the investigation of choice for: - Central/hilar masses accessible via airways - Mediastinal lymph node sampling (stations 2, 4, 7) - Simultaneous diagnosis AND staging (N-staging) - Minimally invasive approach with low morbidity ### Diagnostic Yield for SCLC - SCLC typically arises in central airways - Endobronchial location allows direct visualization + EBUS guidance - Tissue diagnosis + lymph node staging in one procedure - Avoids need for more invasive procedures (mediastinoscopy) ### Comparison Table | Investigation | Sensitivity | Specificity | Invasiveness | Staging Capability | Best Use | | --- | --- | --- | --- | --- | --- | | **EBUS-TBNA** | 90–95% | 99% | Minimally invasive | Yes (N-staging) | Central mass + mediastinal LN | | Mediastinoscopy | 85–90% | 99% | Moderately invasive | Yes | When EBUS fails or contraindicated | | PET-CT | 85–90% | 70–80% | Non-invasive | Yes (M-staging) | Staging, not tissue diagnosis | | Sputum cytology | 40–60% | 95% | Non-invasive | No | Peripheral lesions, screening | **Clinical Pearl:** In SCLC, mediastinal involvement is present in >80% of cases at diagnosis. EBUS-TBNA simultaneously confirms histology and determines N-stage, making it the single most informative first investigation for this presentation. ### Why EBUS-TBNA Over Alternatives - **vs. Mediastinoscopy:** EBUS is less invasive, avoids general anesthesia, and is preferred when airways are involved - **vs. PET-CT:** PET-CT is essential for staging but does NOT provide tissue diagnosis - **vs. Sputum cytology:** Too low sensitivity for central masses; useful only for peripheral lesions **Mnemonic:** **EBUS for Central, Mediastinal Nodes** — When you see a central hilar mass with mediastinal LN on imaging, think EBUS-TBNA first.