Pseudoprogression of Malignant Peripheral Nerve Sheath Tumor in Patient with Neurofibromatosis Type 1, a Case Report.

Pseudoprogression, defined as the radiographic false appearance of disease progression, is not frequently observed in patients with malignant peripheral nerve sheath tumor (MPNST). We report on a case of a patient with neurofibromatosis type 1 (NF1) MPNST pseudoprogression that presented as suspected local recurrence 9.5 years after last treatment. The patient underwent surgical resection following growth of a mass on sequential MRI imaging; surgical pathology, however, showed skeletal muscle with atrophy, fibroadipose tissue, and fat necrosis, without any evidence of tumor. As MPNST survival rates increase, physicians should consider pseudoprogression as a potential presentation after prior treatment.