The histopathology of Langerhans cell histiocytosis.

Selected aspects of the histopathology of Langerhans cell histiocytosis representing diagnostic difficulty and/or controversy are presented with emphasis on the composition of pathological lesions. Lesional cell phenotypes and the factors influencing variations are noted. Features of several skin-based histiocytic disorders, dermatopathic lymphadenopathy and Rosai-Dorfman disease are compared. Associations between Langerhans cell histiocytosis and juvenile xanthogranuloma and malignant disorders are considered. Observations of potential significance in the eventual elucidation of the pathogenesis of these enigmatic diseases are presented.