Figure 6a. Neurogenic tumor: neurofibromatosis type 1 in a 23-year-old man. (a) Oblique sagittal T1-weighted image shows a small mass (solid arrow and arrowheads) involving the inferior aspect of the brachial plexus. Open arrow = axillary artery. (b) Axial T2-weighted image obtained in the proximal arm demonstrates a lobulated mass with areas of central decreased T2 signal intensity typical of a neurofibroma.