Pulmonary Langerhans Cell Histiocytosis

Pulmonary Langerhans Cell Histiocytosis is a chronic progressive interstitial lung disease strongly associated with cigarette smoking.

The images here show an upper lobe-predominant process characterized by irregular cysts and nodules in a peribronchiolar distribution. Differential considerations include pulmonary Langerhans cell histiocytosis and lymphangioleiomyomatosis. Emphysema, which shouldn't be a consideration once you note that the cysts have perceptible walls, is included in some differentials.

The classic teaching is that cysts associated with pulmonary Langerhans cell histiocytosis are less uniform in appearance than those associated with lymphangioleiomyomatosis and that Langerhans cell histiocytosis is associated with nodules (especially early in the course of the disease), while lymphangioleiomyomatosis is not. However, more recent (2003) work suggests that there is considerable overlap between the appearance of lymphangioleiomyomatosis and Langerhans cell histiocytosis and that CT can't be reliably used to differentiate the two.

References

• Bonelli FS, Hartman TE, Swensen SJ, Sherrick A. Accuracy of high-resolution CT in diagnosing lung diseases. AJR Am J Roentgenol. 1998 Jun;170(6):1507-12.
• Koyama M, Johkoh T, Honda O, Tsubamoto M, Kozuka T, Tomiyama N, Hamada S, Nakamura H, Akira M, Ichikado K, Fujimoto K, Rikimaru T, Tateishi U, Müller NL. hronic cystic lung disease: diagnostic accuracy of high-resolution CT in 92 patients. AJR Am J Roentgenol. 2003 Mar;180(3):827-35.