Brachial Plexopathy due to Myeloid Sarcoma in a Patient With Acute Myeloid Leukemia After Allogenic Peripheral Blood Stem Cell Transplantation

Myeloid sarcoma is a solid, extramedullary tumor comprising of immature myeloid cells. It may occur in any organ; however, the invasion of peripheral nervous system is rare. Herein, we report the case of myeloid sarcoma on the brachial plexus. A 37-year-old woman with acute myelogenous leukemia achieved complete remission after chemotherapy. One year later, she presented right shoulder pain, progressive weakness in the right upper extremity and hypesthesia. Based on magnetic resonance images (MRI) and electrophysiologic study, a provisional diagnosis of brachial plexus neuritis was done and hence steroid pulse therapy was carried out. Three months later the patient presented epigastric pain. After upper gastrointestinal endoscopy, myeloid sarcoma of gastrointestinal tract was confirmed pathologically. Moreover, 18-fluoride fluorodeoxyglucose positron emission tomography showed a fusiform shaped mass lesion at the brachial plexus overlapping with previous high signal lesion on the MRI. Therefore, we concluded the final diagnosis as brachial plexopathy due to myeloid sarcoma.