Metastatic malignant peripheral nerve sheath tumour in a patient with neurofibromatosis 1 and review of contemporary systemic treatments.

Malignant peripheral nerve sheath tumours are rare soft tissue sarcomas commonly seen in patients with neurofibromatosis type 1. They typically manifest in the fibrous sheaths of major nerve trunks in the extremities or in an axial location. Presenting symptoms are generally non-specific, including pain and weakness, and survival is dependent on size and location of the tumour. Surgical resection is the primary treatment modality followed by radiotherapy or chemotherapy; however, prognosis is poor. Medications such as tyrosine kinase inhibitors and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathway inhibitors are increasingly being recognised as potentially effective therapy for these malignancies. We report a case of a patient with neurofibromatosis type 1 presenting with a malignant peripheral nerve sheath tumour along the tibial nerve that was initially diagnosed as a muscle strain. We discuss the utility of diagnostic imaging and pathology in correctly identifying this aggressive tumour as well as review the drugs used in her care.