At first, DNA will be extracted from the frozen tumor pieces (neurofibromas and MPNSTs). Together with blood DNA (also rest material), the tumor DNA will be screened with microarray genomic hybridization. This technique allows us to check for chromosomal abnormalities, like amplifications and deletions, with a much higher resolution than traditional cytogenetics. In that way, we can look for recurrent alterations within a certain tumor type and for similarities and differences between benign and malignant tumors.