Differential Expression of Markers in Extensive and Restricted Langerhans Cell Histiocytosis (LCH).

Langerhans cell histiocytosis (LCH) represents a poorly defined pathologic entity characterized by diverse clinical appearence and falling into two major categories namely a restricted and an extensive disease. Since the outcome and the course of the disease is variable, we postulated that this might be reflected by the phenotype of the Langerhans cells. We have selected 11 adult restricted cases and 10 extensive childhood cases and compared the phenotype of LCH cells by immunohistochemistry on paraffin sections. Morphometric analysis indicated a significantly higher expression of histiocytic (CD68, S-100, lysozyme) markers in the adult restricted cases compared to the extensive form of the disease. Both groups were equally positive for LCH marker CD1a and negative for T cell marker CD4. On the other hand, HLA-DR expression was significantly higher in LCH cells of the extensive childhood cases suggesting higher activation. These data suggest that LCH cells have a different phenotype in the extensive childhood and restricted adult LCH where the latter is characterized by a more differentiated histiocytic phenotype.