Fig. 2

A combination of emphysema and patchy mild paucicellular fibrosis characteristic of so-called smoking-related interstitial fibrosis. Against this backdrop, a single piece shows fibrosis with a more stellate configuration, the central focus comprising conventional pigmented (smoking-related) histiocytes and dense collagen fibrosis. This stellate nodule is accompanied by an equally distinctive pattern of paracicatricial airspace enlargement (“scar emphysema”). This combination of features is characteristic of the late fibrotic stage of Langerhans cell histiocytosis, a stage in which diagnostic Langerhans cells have disappeared thus negating the diagnostic value of special stains