Clonal status and clinicopathological features of Langerhans cell histiocytosis.

Some studies have demonstrated that Langerhans cell histiocytosis (LCH) is a neoplastic hyperplasia of Langerhans cells, however some researchers consider that clonality should be assessed in more patients with LCH, both at disease presentation and during the disease course. Monoclonality is a major characteristic of most tumours, whereas normal tissue and reactive hyperplasia are polyclonal. To elucidate the nature of Langerhans cells further, the present study investigated the clinicopathological features and clonality of three cases of LCH in female patients using laser microdissection and a clonality assay, based on X-chromosomal inactivation mosaicism in somatic tissues and polymorphism of the androgen receptor gene. The results indicated that LCH was composed of Langerhans cells with a characteristic morphological appearance, eosinophils, giant cells, neutrophils and foamy cells. Immunohistochemically, the Langerhans cells were positive for CD1a, S-100 protein and vimentin. The clonality assay demonstrated that the Langerhans cells formed a monoclonal population, showing that LCH is neoplastic. We conclude that LCH is characterized by clonal proliferation, although additional studies with larger sample sizes are required to prove this conclusively.