CTICasesPlexiform Neurofibroma of the Mediastinum
Imaging findings
CT demonstrates a large infiltrative soft tissue mass involving the mediastinum around the superior pericardial recess, left main pulmonary artery, aorta, subcarinal region, and interatrial septum. The attenuation of the mass is uniformly low, never exceeding 30 Hounsfield units, giving it a fluid-like or myxoid quality. It infiltrates along multiple mediastinal structures without producing clear nodal masses and without obstructing vascular structures. Vessels course through the mass without obstruction. Biopsies were initially non-diagnostic; more invasive biopsy confirmed plexiform neurofibroma. The patient is 19 years old with no skin findings of neurofibromatosis.
Key takeaways
Plexiform neurofibroma involving the mediastinum is an extremely rare entity that should be added to the differential diagnosis for infiltrative mediastinal masses with very low attenuation (near fluid density). The CT appearance of diffuse low-attenuation infiltration along multiple mediastinal structures without a dominant nodal mass or vascular obstruction is characteristic. It can be confused with lymphangioma or lymphoma. Even without visible cutaneous stigmata of NF1, plexiform neurofibroma should be considered in infiltrative mediastinal lesions with this imaging pattern, particularly if they course along nerve distributions. The mass in this and a similar case at SLU had vessels coursing through it without obstruction.
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