To detect the t(X;18) translocation product, SYT-SSX, total RNA was extracted from frozen archival tumors (15 dermal neurofibromas, 4 plexiform neurofibromas, and 7 MPNSTs) using Trizol.     ///    The RNA was then subjected to reverse-transcriptase polymerase chain reaction (RT-PCR) to specifically amplify SYT-SSX.     ///    "None of the dermal neurofibromas, plexiform neurofibromas, or MPNSTs analyzed were positive for SYT-SSX mRNA. "