3. Measurable disease: Patients must have measurable plexiform neurofibroma(s). For the purpose of this study a measurable lesion will be defined as a lesion of at least 3 cm measured in one dimension. There must be evidence of recurrent or progressive disease as documented by an increase in size or the presence of new plexiform neurofibromas on MRI. Progression at the time of study entry is defined as: