INTRODUCTION
Ewing sarcoma is the third most common bone sarcoma and the second most common malignant bone tumor in children and young adults, with an incidence of 0.1/100 000/year and a median age at diagnosis of 15 years. Most cases arise in the extremities, but axial skeleton and soft tissue origin are possible. [1] Histological diagnosis is supported by the detection of specific gene translocations, generally resulting in EWSR1-FLI1 fusion (EWS-RNA binding protein 1 - Friend leukemia integration 1 transcription factor) or, more rarely, in other ETS genes (Erythroblast Transformation-Specific) such as EWSR1-ERG fusion (ETS Related Gene). [2] With the introduction of multiagent perioperative chemotherapy, including vincristine, doxorubicin, cyclophosphamide, ifosfamide and etoposide, 5-year OS increased to 65-70% in localized disease. [1] About 25% of patients present at diagnosis with advanced disease at diagnosis: most frequently involved sites are lung, bone and bone marrow. For this reason, an accurate skeletal staging with positron emission tomography (PET-CT) is mandatory and, in doubt cases, it must be completed with bone marrow biopsy and aspirate. [3] Five-year overall survival in patients with metastatic disease ranges from 20 to 40% according to metastases site, with bone localizations conferring a poorer prognosis. [4]
Moreover, Ewing sarcoma recurrence with bone marrow involvement has been associated with very poor survival and unavoidable fatal outcome, in contrast to patients with multiple bone metastases but no marrow involvement [5]. High-dose ifosfamide has been recently demonstrated to be highly effective on recurrent disease, with other active regimens being cyclophosphamide and topotecan, temozolomide and irinotecan, and gemcitabine and docetaxel. [6] Here we present the case of a young male patient affected by extremity Ewing sarcoma recurring with bone marrow infiltration causing severe pancytopenia 15 months after the end of adjuvant chemotherapy.