Secondly, the group of MPNSTs will be subdivided in tumors derived from NF1 microdeletion patients and tumors from patients with an intragenic mutation. Recurrent chromosomal gains and losses will be compared between the 2 groups. This will show us if the mechanism of tumor development and progression is different in NF1 microdeletion patients. In cooperation with the group of André Bernards and Karen Cichowski, we will try to elucidate the role of the NF1 microdeletion in the development of neurofibromas. Our group will collect all tumor samples and grow Schwann cells and fibroblasts out of these tumors. The frozen vials with tumor pieces and cultured cells will be encoded and provided to these labs as part of our collaboration.