Pulmonary histiocytosis: beyond Langerhans cell histiocytosis related to smoking

To review the imaging findings for the different types of pulmonary histiocytosis. In particular, in addition to the well-known pulmonary Langerhans cell histiocytosis related to smoking and its possible appearance in nonsmokers, we focus on non-Langerhans cell histiocytosis in Rosai-Dorfman disease and Erdheim-Chester disease. We also review the etiopathogenesis, histology, clinical presentation, and treatment of pulmonary histiocytosis.

Langerhans cell histiocytosis, Rosai-Dorfman disease, and Erdheim-Chester disease are idiopathic diseases in which the proliferation and infiltration of histiocytes is the histologic finding that confirms the diagnosis. Langerhans cell histiocytosis manifests as nodules and cysts that spare the costophrenic angles; it typically appears in smokers. Although it is uncommon in nonsmokers, Langerhans cell histiocytosis should also be considered in nonsmokers treated with chemotherapy and radiotherapy in whom cavitated nodules appear and should be included in the differential diagnosis together with metastatic disease and opportunistic infections. Rosai-Dorfman disease and Erdheim-Chester disease present with less specific thoracic findings such as adenopathies, interstitial thickening, and pleural effusion. In Erdheim-Chester disease, the characteristic extrathoracic manifestations are usually key for the diagnosis.