Absence of FLT3 and JAK2 (V617F) Mutations in Langerhans Cell Histiocytosis

Langerhans cell histocytosis (LCH) is a neoplasm of histiocytic cells believed to be derived from cells of the dendritic system, but the disease pathogenesis is unknown. FMS-like tyrosine kinase 3 (FLT3) is a type III receptor tyrosine kinase that is expressed on the surface of hematopoietic stem cells and plays an important role in normal hematopoiesis. Recently, FLT3 has been shown to play a role in regulating dendritic cell development and elevated levels FLT3-ligand was found in the serum of LCH patients. Therefore we evaluated 14 cases of LCH for FLT3 mutations by PCR analysis of genomic DNA, obtained from formalin-fixed paraffin-embedded tissue samples, followed by PAGE for deletions or internal tandem duplications using a commercially available kit (InVivoScrib Technologies, San Diego, CA). There were 7 males and 7 females with a mean age of 25.1. The tissues involved included bones, lymph nodes, bone marrow, breast, lungs and various soft tissues. No mutations in FLT3 were identified in any of the 14 patient samples. In the same patient population we also looked at the JAK2 (V617F) mutation, which has been found in patients with myeloproliferative disorders other than chronic myeloid leukemia and which has not yet been evaluated in LCH by a single strand conformation polymorphism assay using a commercially available kit (Ipsogen, New Haven, CT). There was no JAK2 V617F mutation in any of the 14 cases. These results suggest that FLT3 and JAK2 V617F mutations do not play a role in the pathogenesis of LCH.