Periosteal Ewing Sarcoma: Imaging Features and Clinical Outcomes in 7 Patients.

OBJECTIVE: The aim of this study was to describe imaging features, treatment, and prognosis of patients with periosteal Ewing sarcoma (PES). MATERIALS AND METHODS: Seven patients with PES treated between 2001 and 2020 were studied retrospectively for presenting symptoms, imaging features, treatment, and prognosis. RESULTS: Among the 7 patients (mean age, 27.3 years) with local pain and/or mass of less than 6 months duration, 4 were males and 3 females (1.3:1). These surface tumors involved 3 long bones and 4 pelvic bones. Radiographs showed cortical erosions with 2 and CT with 4 long bone tumors. All 7 surface tumors showed normal marrow on MRI, and 4 tumors demonstrated normal marrow activity on 18FFDG fluorodeoxyglucose PET-CT. The only exception was a PES involving iliac bone with thin cortex and marrow extension, which demonstrated hypermetabolic marrow activity. All patients were treated initially with chemotherapy and optional radiation treatment with complete tumor resolution of a tibial PES in 1 patient. The remaining 2 patients with long bone PES had tumor resection and limb-salvage surgery and the 4 patients with pelvic bone PES had hemipelvectomy after chemotherapy/radiation treatment. Five patients were disease-free with long-term survival. A patient with a long bone PES and solitary lung metastasis at onset had tumor resection and metastasectomy with complete recovery without tumor recurrence. The 2 patients with pubic bone PES had complete recovery without tumor recurrence; however, the remaining 2 patients with iliac bone PES developed distant metastases and died within 2 years of diagnosis. CONCLUSIONS: Periosteal Ewing sarcoma arises in periosteum of bone and spares medullary cavity. As compared with its intramedullary counterpart, the tumor has better prognosis with long-term survival. Rarely, the surface tumor arising at a bone with thin cortex, such as iliac bone or scapula, may have medullary involvement. We have described our experience in diagnosis and clinical management in 7 patients of this rare surface variant of the more common intramedullary Ewing sarcoma.