Figure 3.

a) Pulmonary Langerhans’ cell histiocytosis (PLCH) is characterised by an increased number of CD1a+ Langerhans’ cells in the bronchiolar wall (200×). b) In the early/active phase of PLCH stellate cellular nodules with a bronchiolocentric distribution can be seen (haematoxylin and eosin, 10×). c) A stellate fibrotic nodule suggestive of healed PLCH is present on the left and is associated with an extensive accumulation of smoker's macrophages (haematoxylin and eosin, 20×). d) Classical example of PLCH in its mature phase consisting of multiple bronchiolocentric cellular nodules, some of which are fibrotic and irregularly cavitated (haematoxylin and eosin, 10×). e) A high-resolution computed tomography image at the level of the upper lobes showing numerous irregularly marginated bilateral nodules; a few cysts are visible. f) Chronic PLCH showing stellate scars with paracicatricial emphysema (haematoxylin and eosin, 40×).