Mediastinum > Nervesheath

Malignant Tumor of Nerve Sheath Origin:


This tumor was formerly referred to as a malignant schwannoma or neurofibrosarcoma. The lesion is rare 5-10% of all soft tissue sarcomas, and intrathoracic MPNSTs are particularly rare [3] (the lesion is rare and accounts for less than 1% of all mediastinal neurogenic neoplasms). It is an aggressive, locally invasive, and metastasizing spindle cell sarcoma that typically arises from a simple or plexiform neurofibroma (and rarely, if ever, from a pre-existing schwannoma). Patients with neurofibromatosis (NF1) are at an increased risk for this tumor (about 20% to 50% of cases occur in patients with NF1 and the life time prevalence is about 10%), and have a significantly worse prognosis (5-year survival of approximately 34-60% [3]). Patients typically present around 40-50 years of age (NF1 patients present at a younger age [3]), with pain, a rapidly enlarging mass, or nerve deficit. The lesion frequently metastasizes hematogenously to the lungs.


The lesion is typically large by the time of presentation. Low attenuation areas within the mass are related to the presence of hemorrhage and necrosis.

On MR, findings which suggest a MPNST rather than a neurofibroma include a large lesion (>5cm), peripheral enhancement pattern, the presence of perilesional edma-like zone, and intratumoral cystic change [3]. The lesion is intensely FDG avid on PET imaging [3].

(1) Chest 1997; Strollo DC, et al. Primary mediastinal tumors. Part II: Tumors of the middle and posterior mediastinum. 112: 1344-57

(2) AJR 2007; Bredella MA, et al. Value of PET in the assessment of patients with neurofibromatosis type I. 189: 928-935

(3) AJR 2016; Pavlus JD, et al. Imaging of thoracic neurogenic tumors. 207: 552-561

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