3. Patients must have measurable PN by direct physical examination (documented by clinical measurement of tumor and serial photography) or by imaging studies. Most patients will have tumors that can be measured by magnetic resonance imaging (MRI), however, some patients may have cosmetically disfiguring PN which would be best measured clinically and with serial photography throughout treatment and follow-up. A measurable lesion is one whose size can be quantified in at least 2 dimensions. There must be evidence of recurrent or progressive disease as documented by an increase in size or the presence of new lesions on MRI. Progression is defined as the appearance of new tumors or a measurable increase in the sum of the product of the two longest perpendicular diameters of the index lesion(s) over a time period < 12 months prior to evaluation for this study. For purposes of this study, index PN lesions will be those PNs evaluated as the most life-threatening, debilitating, cosmetically disfiguring, and/or most easily measured.