A 45-year-old man presents with mild haemoptysis. Chest X-ray shows a round, well-defined, 3 cm opacity in the left mid-zone with a crescent of air around its superior and lateral border. Which sign is described?
- A Air crescent sign ✓
- B Monad sign
- C Deep sulcus sign
- D Luftsichel sign
Correct answer: A. Air crescent sign
Explanation
The air crescent sign is a crescent of air surrounding a rounded mass, classically seen in aspergilloma (fungus ball) within a pre-existing cavity. The monad sign refers to the appearance of a fungus ball moving with position. The deep sulcus sign indicates pneumothorax in supine patients. Luftsichel sign is a crescent of air around a collapsed left upper lobe.
Reference: Felson's Principles of Chest Roentgenology, 4th ed.
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