Plexiform neurofibroma and potential malignant peripheral nerve sheath tumor in neurofibromatosis t1

Coronal T2 weighted image from a whole body MRI (image 1) shows extensive plexiform neurofibromas involving the upper extremities. Post contrast T1 weighted MRI (image 2) shows a focal area of enhancement (arrow) of one portion of the plexiform neurofibroma concerning for degeneration to a malignant peripheral nerve sheath tumor. PET/CT (image 3) highlights FDG uptake (arrow) within the small tumor. Malignant peripheral nerve sheath tumor is a type of sarcoma. 50 to 60% of patients with malignant peripheral nerve sheath tumor have neurofibromatosis type I.

Why you should join Figure 1

• Share your knowledge with our global community of healthcare professionals
• Get help from experts in your field
• Learn from our library of real-world cases and quizzes

Similar cases

Axial T2-W image in a child with neurofibromatosis type 1, shows a large plexiform neurofibroma of the pelvis. The plexiform neurofibroma is composed of multiple lesions, each with a characteristic target appearance. The target appearance occurs because the neurofibroma contains a central area of dense collagen. The target sign is not always present in plexiform neurofibromas. However, if a tumor loses the sign, this is considered to be a finding of degeneration to a malignant peripheral nerve sheath tumor. Other findings of malignant degeneration include heterogeneous enhancement, lobulation of the tumor, and rapid change in size, and irregular margins.

Axial T1-weighted (image 1) and axial T1-weighted postcontrast (image 2) MR images highlighting the malignant peripheral nerve sheath tumor (arrow). MRI features that can be used to help differentiate a malignant peripheral nerve sheath tumor from a plexiform neurofibroma include loss of a target appearance on T2-weighted images, inherent T1 hyperintense signal, and heterogeneous enhancement.

Coronal FS T2-weighted MRI of the posterior knee in a teenager with neurofibromatosis type I shows multiple elongated fluid-signal intensity lobules along the expected courses of the sciatic, tibial, & common peroneal nerves. Central hypointense foci (which create a “target appearance” in cross-section) are seen in some of the lesions (white arrows), typical of plexiform neurofibromas.