Primary Histiocytic Disorders of the Lung

Abstract

The primary histiocytic disorders of the lung, pulmonary Langerhans cell histiocytosis, Erdheim Chester Disease, and Rosai-Dorfman-Destombes Disease are rare inflammatory neoplasms that have recently been found to harbor growth and survival-promoting mutations in key signaling pathways of myeloid cells. These discoveries have revolutionized our understanding of disease pathogenesis in these disorders and revealed promising new molecular targets for therapy. There are a number of secondary histiocytic disorders associated with reactive accumulation of histiocytes due to infections (e.g. tuberculosis), storage disorders (e.g. Gaucher, Niemann Pick Disease, crystal storing histiocytosis), or various other conditions (bronchiolar obstruction, nonspecific interstitial pneumonia, and Whipple disease) that will be not be covered here. Malignant histiocytic conditions (e.g. histiocytic sarcoma, primary Langerhans sarcoma, follicular dendritic cell sarcoma, interdigitating dendritic cell sarcoma) are also beyond the scope of this review. We will instead focus on these three fascinating ‘benign metastasizing’ conditions of adults, that have recently been discovered to share common genetic and pathogenic origins.