Figure 25.

A, Pulmonary Langerhans cell histiocytosis. Generally seen in young smokers (most commonly between 20 and 40 years of age). Cysts are seen predominantly in upper and middle lobes, are variable in size, are thick- or thin-walled, and have bizarre shapes. The costophrenic angles are spared. The intervening lung parenchyma exhibits architectural distortion. B, Langerhans cell histiocytosis pathologic findings. (a) Low-power histology shows a stellate nodule composed of fibrosis with some cellular infiltrates. At the edges of the fibrotic scar is paracicatricial emphysema, giving some cystic appearance. (b) High-power shows a cellular proliferation of Langerhans cells.