Interferon is a drug that is used for different types of tumors as well as for hepatitis. It has been used in the treatment of plexiform neurofibromas (PNF) with some subjects showing improvement in symptoms and/or a decrease in the size of the tumor. Most subjects had no further growth of their tumor while on the PEG-Intron. The drug used in this study is PEG (pegylated)-Intron. PEG-Intron is a long acting form of interferon which keeps the drug from being broken down in the body for a longer period of time and potentially could be more effective than the short-acting interferon. PEG-Intron has been approved by the Food and Drug Administration (FDA) for the treatment of Hepatitis C.