A 45-year-old man with a history of asbestos exposure presents with progressive dyspnea and chest pain. HRCT chest shows bilateral lower lobe predominant interstitial thickening with pleural plaques and a 3 cm nodule in the right lower lobe. Which of the following is the most likely diagnosis?

## Diagnosis: Asbestosis with Incidental Lung Cancer ### Clinical and Radiological Features **Key Point:** The combination of asbestos exposure history, bilateral lower lobe interstitial fibrosis, pleural plaques, and a solitary nodule is pathognomonic for asbestos-related lung disease with superimposed malignancy. ### HRCT Findings in Asbestosis | Feature | Asbestosis | Silicosis | Talcosis | |---------|-----------|----------|----------| | Distribution | Bilateral lower lobe | Upper lobe | Variable | | Pleural involvement | Plaques, thickening | Rare | Rare | | Parenchymal pattern | Irregular interstitial | Nodular | Nodular | | Associated malignancy risk | High (lung cancer, mesothelioma) | Moderate | Low | **Clinical Pearl:** Asbestos exposure increases lung cancer risk 5-fold and mesothelioma risk 200-fold. The presence of pleural plaques is virtually diagnostic of asbestos exposure. ### Why This Patient Has Asbestosis 1. **Occupational exposure:** 10+ years of asbestos exposure is a strong risk factor 2. **Pleural plaques:** Highly specific for asbestos; appear as focal thickening on visceral or parietal pleura 3. **Lower lobe predominance:** Typical distribution for asbestos-related fibrosis 4. **Nodule in context:** Asbestos-exposed workers have significantly elevated lung cancer risk; a new nodule warrants biopsy or follow-up imaging **High-Yield:** Asbestos-related lung disease includes: - Asbestosis (parenchymal fibrosis) - Pleural plaques (most common finding) - Pleural thickening - Pleural effusion - Lung cancer - Mesothelioma ### Management Approach ```mermaid flowchart TD A[Asbestos exposure + HRCT findings]:::outcome --> B{Pleural plaques present?}:::decision B -->|Yes| C[Confirm asbestosis]:::action C --> D{Nodule present?}:::decision D -->|Yes| E[Evaluate for malignancy]:::action E --> F[Biopsy or PET-CT]:::action F --> G[Staging if cancer confirmed]:::outcome D -->|No| H[Surveillance imaging]:::action ``` **Tip:** Any new or enlarging nodule in an asbestos-exposed worker should be treated as lung cancer until proven otherwise.