Case Report Rare case of small size Extraskeletal Ewing Sarcoma arising from the median nerve with paresthesia Khodamorad Jamshidi, Alireza Mirzaei * , Abolfazl Bagherifard, Mehrdad Bahrabadi Bone and Joint Reconstruction Research Center, Shafa Orthopedic Hospital, Iran University of Medical Sciences, Tehran, Iran article info Article history: Received 27 February 2016 Received in revised form 7 June 2016 Accepted 8 June 2016 Available online xxx 1. Introduction Ewing sarcoma is the second most common type of primary malignant bone tumor in childhood and adolescence. Almost one fourth of this aggressive tumor originates from soft tissue, regar- ded as Extraskeletal Ewing Sarcoma (EES) [1]. EES is usually seen in young adults with a rapidly growing mass in trunk, paraspinal muscles or extremities. However, EES of upper extremity is un- common and only a small number of reported cases has been devoted to upper extremity EES. In this regard, EES of shoulder and finger has been reported [2,3]. EES in the proximity of the sciatic nerve has also been reported [4]. To our knowledge, no case of EES in median nerve has been previously published. The pres- ence of this tumor in close association with the brachial plexus is important as the compression on neural elements can invoke peripheral neuropathy, further complicating the already difficult diagnostic puzzle. In addition, regarding the different treatment and prognosis of resembling tumors including schwanoma, neurofibroma, embryonal rhabdomyosarcoma, lymphoma and neuroblastoma, the differentiation of this tumor from other le- sions is very important. Inappropriate diagnosis of such tumors leads to an impaired therapeutic approach resulting in poor outcome of tumor. We here discuss a rare EES case of median nerve and its man- agement approach in order to avoid potential confusion in the assessment of this highly malignant tumor which leads to the better management of similar cases. 2. Report of the case A 29-year-old male with the symptoms of left hand pares- thesia, a tender nodule on the medial side of left arm close to his anterior axillary fold, and no previous medical history of any notable disorder, was referred to our center. Disease manifesta- tion started two months earlier as paresthesia of left third and forth fingers, which made the diagnosis of schwanoma or neurofibroma highly probable [5,6]. After about one month, he noticed a small tender mass in the upper part of left arm. At this time, electrodiagnostic studies showed left median nerve axonal neuropathy caused by compression at axilla. A shoulder MRI was requested which did not help with the diagnosis, but the arm MRI showed a small mass less than 1 cm with low signal in T1- weighted images and high signal in T2-weighted images next to the axillary vessels (Figs. 1 and 2). Considering the median nerve involvement and the small size of the mass on MRI resembling clinical figure of schwanoma or neurofibroma we scheduled the patient for an excisional biopsy. Through direct longitudinal incision over the intended lump, along to the neurovascular bundle, a mass with small rubbery purple soft tissue structure, placed in the median nerve was observed. According to our knowledge, the mass did not resemble to the neuroma or schwanoma. Nevertheless, marginal excision of the mass was performed. The size of the tumor was less than 1 cm in its largest diameter and had a gross dark red appearance. The specimen was sent for histopathology analysis. After per- forming usual histopathology staining methods, monotonous small round blue cells were visible (Fig. 3). Immunohistochemical staining of relevant markers including CD99, smooth muscle an- tigen (SMA) and Caldesmin was performed. The tumor was posi- tive for CD99, but negative for Caldesmin and SMA (Fig. 3). However, since it was an unusual and rare case, patient's paraffin blocks were sent for cytogenetic analysis in order to evaluate the translocation of t(11;22) (q24;q12) which is a defining feature of * Corresponding author. Shafa Orthopedic Hospital, Mojahedin Islam Avenue, Shohada Sq, Tehran, Iran. Fax: þ98 (21) 33542020. E-mail address: mirzaeialireza26@gmail.com (A. Mirzaei). Contents lists available at ScienceDirect Journal of Orthopaedic Science journal homepage: http://www.elsevier.com/locate/jos http://dx.doi.org/10.1016/j.jos.2016.07.017 0949-2658/© 2016 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved. Journal of Orthopaedic Science xxx (2016) 1e3 Please cite this article in press as: Jamshidi K, et al., Rare case of small size Extraskeletal Ewing Sarcoma arising from the median nerve with paresthesia, Journal of Orthopaedic Science (2016), http://dx.doi.org/10.1016/j.jos.2016.07.017