Langerhans Cell Histiocytosis
Langerhans cell histiocytosis (LCH) formerly known as pulmonary eosinophilic granuloma is currently regarded by the World Health Organization as a clonal neoplastic proliferation of histiocytes. However, adult variants may represent reactive processes, usually associated with cigarette smoking. Most patients with LCH are either current or former smokers. Radiographically, LCH shows a predilection for the mid to upper lung zones, presenting on high-resolution CT of the chest as nodular lesions, with or without cystic change. Rarely, regional lymph nodes may be affected by the diseases process. The histopathological hallmark of the disease are star-shaped fibrotic lesions containing Langerhans histiocytes. These cells are cells with abundant pale cytoplasm and a distinctively folded or grooved nuclei. Typically, these cells will stain positively with CD1a and the S-100 protein.