 - Patients must have a progressive plexiform neurofibromas. Progression at the time of study entry is defined as: Presence of new plexiform neurofibromas on MRI or CT, OR A measurable increase of the plexiform neurofibroma or equal to 20 increase in the volume, or a or equal to 13 increase in the product of the two longest perpendicular diameters, or a or equal to 6 increase in the longest diameter over the last two consecutive scans MRI or CT, or over the time period of approximately one year prior to evaluation for this study. 