Cavitation, Thin-walled Cysts and Bullae, their Association with Tumours. Emphysema. Fat and Calcification. Spurious Tumours. Intravascular, Pulmonary Interstitial & Mediastinal Gas, and Pneumoperitoneum.

Tuberculosis tends to cause single or multiple cavities, often with evidence of surrounding disease and bronchopneumonic spread elsewhere in the lungs. Anterior cavities at the lung apices are nearly always accompanied by others posteriorly, and in their absence, one should think of mycobacteria. A breaking down carcinoma typically gives rise to eccentric cavitation, an irregular wall and a necrotic mass. Most thin-walled air filled cystic looking spaces in the lungs are bullae or pneumatocoeles, and even those that become infected usually have thin walls. Most cavitating neoplasms have thick or thickened walls, which are often irregular on their inner and/or outer aspects. Secondary lung deposits may cavitate, even in the absence of chemotherapy.