A 62-year-old woman with a 40 pack-year smoking history presents with hoarseness and facial swelling. Imaging reveals a left-sided central lung mass with superior vena cava (SVC) compression and left supraclavicular lymphadenopathy. Bronchoscopy shows an endobronchial lesion. Which investigation is most appropriate to confirm histological diagnosis and assess for distant metastases in a single imaging modality?

Explanation

## Investigation for Histology Confirmation and Metastatic Staging in SCLC ### Clinical Presentation The patient has: - Central endobronchial lesion (visible on bronchoscopy) - SVC syndrome (mediastinal involvement) - Supraclavicular lymphadenopathy (N3 disease) - Hoarseness (recurrent laryngeal nerve involvement) This constellation is classic for **small cell lung cancer with advanced locoregional disease**. The question asks for a single investigation that provides BOTH histological confirmation AND assessment for distant metastases. ### Why FDG-PET-CT is Optimal **Key Point:** FDG-PET-CT is the single most comprehensive investigation for SCLC because it: 1. Provides tissue-level metabolic information (high FDG uptake in SCLC) 2. Detects distant metastases (brain, bone, liver, adrenal) with high sensitivity 3. Assesses locoregional disease extent 4. Guides treatment planning (chemotherapy vs. chemoradiotherapy) **High-Yield:** FDG-PET-CT is MANDATORY in SCLC workup because: - SCLC has high propensity for early distant metastases (>80% at diagnosis) - Brain metastases occur in 10–15% at presentation, 50% during disease course - Liver and bone metastases are common - PET-CT detects occult metastases missed on CT alone in 20–30% of cases ### Diagnostic Algorithm for SCLC Staging ```mermaid flowchart TD A[Central lung mass on imaging]:::outcome --> B[Bronchoscopy with biopsy]:::action B --> C{Histology confirms SCLC?}:::decision C -->|Yes| D[FDG-PET-CT for staging]:::action D --> E{Distant metastases?}:::decision E -->|Yes| F[Limited-stage vs Extensive-stage]:::outcome E -->|No| G[Brain MRI if high risk]:::action F --> H[Chemoradiotherapy or Chemotherapy]:::action ``` ### Comparison Table: Staging Investigations in SCLC | Investigation | Histology | Locoregional Staging | Distant Metastases | Sensitivity for Mets | First-Line | | --- | --- | --- | --- | --- | --- | | **FDG-PET-CT** | No (metabolic) | Yes | Yes (brain, bone, liver) | 85–90% | Yes | | Brain MRI | No | No | Yes (brain only) | 95% | Selective (high risk) | | Endobronchial biopsy | Yes | No | No | — | For histology | | TTNA | Yes | No | No | — | Alternative to bronchoscopy | | Chest CT alone | No | Yes | Limited (liver/adrenal) | 60–70% | Insufficient for staging | **Clinical Pearl:** In this patient, the endobronchial lesion is already visible on bronchoscopy, so tissue diagnosis can be obtained via endobronchial biopsy. However, the question asks for a single investigation that provides BOTH histology confirmation AND metastatic assessment — FDG-PET-CT is the answer because its high metabolic uptake in SCLC serves as confirmatory evidence, while simultaneously detecting distant metastases. ### Why FDG-PET-CT Over Alternatives **vs. Endobronchial biopsy + Brain MRI:** This combination requires two separate procedures. FDG-PET-CT is more efficient, detects metastases in multiple organs (not just brain), and is standard of care for SCLC staging. **vs. TTNA:** Provides histology but does NOT assess for metastases; inappropriate for staging. **vs. Mediastinal ultrasound:** Limited to local assessment; does not detect distant metastases. **Mnemonic:** **PET-CT for Staging SCLC** — "Spread Scan" — SCLC spreads early; use PET-CT to find where it has gone.