A 68-year-old woman with a history of smoking presents with persistent cough and haemoptysis for 3 weeks. Chest X-ray shows a 3 cm peripheral lung nodule. Which is the most appropriate next investigation to characterize this lesion and guide management?

## Investigation of Choice for Characterization of Lung Nodule **Key Point:** In a patient with a suspicious lung nodule (>2.5 cm, peripheral location, risk factors for malignancy), **high-resolution CT (HRCT) chest with contrast** is the investigation of choice for characterization. PET-CT is added if CT features are indeterminate or suggest malignancy. **High-Yield:** Lung nodule characterization algorithm: 1. **HRCT chest with contrast** — assesses nodule size, morphology, density, margins, enhancement pattern 2. **PET-CT** — if nodule shows indeterminate features or imaging suggests malignancy (high SUV uptake indicates metabolic activity) 3. **Tissue diagnosis** — bronchoscopy, transthoracic biopsy, or surgical resection based on imaging and clinical probability **Clinical Pearl:** A nodule >2.5 cm in a smoker with haemoptysis has a high pretest probability of malignancy. HRCT can identify benign features (fat density, calcification patterns) or suspicious features (spiculation, pleural indentation). PET-CT adds metabolic information (FDG uptake) to guide biopsy vs. surveillance. **Mnemonic for suspicious nodule features — SPICULATED:** - **S**piculation (irregular margins) - **P**leural indentation - **I**rregular borders - **C**avitation (rare in benign lesions) - **U**pstream atelectasis - **L**ower lobe location - **A**ir bronchogram - **T**ail sign - **E**nhancement with contrast - **D**ensity (solid, not ground-glass) ## Imaging Modalities for Lung Nodule Evaluation | Modality | Role | Sensitivity | Specificity | |----------|------|-------------|-------------| | Chest X-ray | Initial detection, screening | 60–70% | Variable | | HRCT chest | Characterization, morphology, density | 90–95% | 70–80% | | PET-CT | Metabolic activity, staging if malignant | 85–95% | 70–90% | | Bronchoscopy | Tissue diagnosis (central lesions) | 30–60% | High | | Transthoracic biopsy | Tissue diagnosis (peripheral lesions) | 85–95% | High | [cite:Harrison 21e Ch 242]