NF1 is characterized by the appearance of multiple tumors of the peripheral nerve, and occasionally the malignant transformation of these tumors. The only available but unsatisfying therapy is surgical tumor resection. The purpose of this study is the preclinical testing of multiple available tyrosine kinase inhibitors for NF1-associated MPNST using in vitro and in vivo systems. Test systems are to be established. Molecular analysis of the targeted receptor tyrosine kinases will show the incidence of alterations in the receptors and provide a profile of activation of the associated pathways in MPNST. According to the patterns of receptor tyorsine kinase receptor activity appropriate inhibitors will be tested for effects on tumor growth. The findings will substantiate causal therapy attempts based on the tumor specific tyrosine kinase receptor activity profile.