In some widespread pulmonary diseases, cystic lesions are significant imaging features, or they may represent the characteristic element. Therefore, the diagnosis of these pulmonary diseases should be based on number, morphology and distribution of the cysts, on the possible detection of associated lung parenchymal abnormalities and on the clinical and medical history.

The term “cyst” indicates a round circumscribed space, usually less than the diameter of centimeter, surrounded by an epithelial or fibrous wall of variable thickness [1]. In TC scans, the cyst appears as an oval area of low parenchymal attenuation, showing well-defined interface with the surrounding lung parenchyma; they may have a variable wall thickness, although – in most cases – they are usually limited by a thin wall (< 2 mm). Pulmonary cysts may occur with or without signs of emphysema. Their content is...

1. Histiocytosis X In this disease, cysts are produced by the progressive increase of the central air component of “star nodules”, which arise from the proliferation of peri-bronchiolar infiltrates of Langerhans cells. These regulate the mucosal immunity of the airways; cigarette smoking may be a determining factor in the accumulation and activation of these cells [2], through the increased levels of cytokines such as GMCSF and βTGF. Morphologically, these bronchiole-centric lesions evolve from micro- and macro-nodules with a high cellular component, in lesions with poor...

Pulmonary cystic diseases may have heterogeneous appearance on imaging. To obtain a correct diagnosis, a precise and accurate description of features of cysts is very important; in addition to features of pulmonary cysts, radiologists should never underestimate the concomitant parenchymal abnormalities.

Dr. Daniele Carmelo Caltabiano, Radiology Resident, University of Catania (Italy): [email protected] Dr. Valeria Costanzo, Radiology Resident, University of Catania (Italy): [email protected] Dr. Luca Mammino, Radiology Resident, University of Catania (Italy): [email protected] Dr. Virginia Vindigni, Regional Centre for Interstitial and Rare Diseases, Department of Clinical and Experimental Medicine, University of Catania Dr. Sebastiano Torrisi, Regional Centre for Interstitial and Rare Diseases, Department of Clinical and Experimental Medicine, University of Catania Dr. Roberta Rosso, Regional Centre for Interstitial and Rare Diseases, Department of Clinical and Experimental Medicine,...

1. Genereux GP. The end-stage lung: pathogenesis, pathology, and radiology. Radiology 1975;116:279–289. 2. Xaubet A, Agust´ı C, Picado C, Guere´ quiz S, Martos JA, Carrio´ n M, Agust´ı-Vidal A. Bronchoalveolar lavage analysis with anti-T6 monoclonal antibody in the evaluation of diffuse lung diseases. Respiration 1989;56:161–166. 3. Colby TV, Lombard C. Histiocytosis X in the lung. Hum Pathol 1983;14:847–856. 4. Koyama M, Johkoh T, Honda O et al (2003) Chronic cystic lung disease: diagnostic accuracy of high-resolution CT in 92 patients. AJR Am J Roentgenol 180:827–835....