The scientific challenge of Langerhans cell histiocytosis.

Langerhans cell histiocytosis is difficult to study because of its rarity. Although recent studies indicate that it may be a clonal proliferation this does not prove that it is a malignant tumour. New methods for culturing dendritic cells and their precursors provide the opportunity to resolve issues relating to clonality, underlying genetic lesions and functional abnormalities in LCH or other lesional cells. The expression of the CD1a antigen on LCH cells provides a target for therapy.