Patients with NF1 microdeletion develop more neurofibromas at a younger age, and have an increased risk of malignant peripheral nerve sheath tumors (MPNSTs). We postulated that the increased risk of malignancy could be due to inactivation, in addition to NF1, of a second tumor suppressor gene located in the typical 1.4-Mb microdeletion found in most of the microdeleted patients. We investigated the expression of NF1, the other 16 protein-coding genes and the 2 microRNAs located in the 1.4-Mb microdeletion by means of real-time quantitative reverse-transcription polymerase chain reaction (RT-PCR) in a large series of human dermal and plexiform neurofibromas and MPNSTs. Five genes were significantly upregulated: OMG and SUZ12 in plexiform neurofibromas and ATAD5, EVI2A and C17orf79 in MPNSTs. More interestingly, two genes were significantly downregulated (RNF135 and CENTA2) in tumor Schwann cells from MPNST biopsies and in MPNST cell lines. This study points to the involvement of several genes (particularly RNF135 and CENTA2) in the increased risk of malignancy observed in NF1-microdeleted patients.