Histiocytic Lesions of the Lung

Histiocytic disorders of the lung cover a wide range of conditions that can involve the lung in isolation or as part of a systemic process. These diseases are caused by proliferative abnormalities of cells of the mononuclear phagocyte system and their principal cell, the histiocyte. Histiocytes comprise a group of immune cells, including antigen-processing macrophages and antigen-presenting dendritic cells (Favara et al., Med Pediatr Oncol 29:157-166, 1997; McClain et al., Hematology Am Soc Hematol Educ Program 283-296, 2004; Wang et al., Semin Diagn Pathol 24: 162-182, 2007). Histiocytic disorders, both benign and malignant, are relatively rare in the bronchopulmonary system and can cause a spectrum of conditions with clinical behavior ranging from spontaneous regression to life-threatening syndromes. Some of these disorders present as primary lesions and are of unknown etiology, while others are the result of a histiocytic response to a known cause.