Dendritic Cell Neurofibroma with Pseudorosettes Lacks Mutations in Exons 1-15 of the Neurofibromatosis Type 2 Gene
Dendritic cell neurofibroma with pseudorosettes (DCNWPR) is a recently proposed variant of neurofibroma with a distinctive microscopic appearance that is produced by a pseudorosette pattern formed by small, dark, lymphocyte-like cells (Type I cells) arranged concentrically around larger cells, with pale-staining vesicular nuclei and copious faintly eosinophilic cytoplasm (Type II cells). Although DCNWPR appears not to be associated with neurofibromatosis (NF), 1 patient with DCNWPR has been described and suggested to have a form of NF because of multiple skin lesions, with 2 of them being DCNWPR as confirmed histologically. The aim of this study was to find out whether the neurofibromatosis type 2 (NF2) gene is mutated in DCNWPR. Seven histologically proven cases of DCNWPR, from which a substantial amount of archival paraffin-embedded material was available, were selected for this study. Three cases have been previously reported, including the intraneural lesion, and 4 cases were newly identified. There were 3 female and 4 male patients, ranging in age from 30 to 61 years (median, 48 yrs). All patients clinically presented with a small solitary lesion that was clinically diagnosed as fibroma or neurofibroma, and none of the patients had signs of NF. Follow-up was known for 6 patients (range, 1-5 yrs; median, 2.5 yrs) and was uneventful in each case. Microscopically, all lesions fulfilled the criteria for DCNWPR. Exons 1 to 15 of the NF2 gene were amplified by PCR using primers previously published. The amplified fragments were purified and sequenced. The obtained sequences were computer analyzed and compared with the data of the GenBank database. No mutation was identified in 5 analyzed samples from which suitable DNA had been extracted. DCNWPR appears to have no mutation in exons 1-15 of the NF2 gene. Given the relatively small number of cases studied, it seems premature to declare that a mutation of the NF2 gene is not involved in DCNWPR, as the possibility cannot be excluded that mutations were present but remained undetected because they occurred in exons that were not examined.