**2.3 Ewing's sarcoma**

Ewing's sarcoma is an exception to all the bone tumors, because bone tumors are mostly mesenchymal in origin, but Ewing's sarcoma is reported to have neuroectodermal precursor cells [7]. It has been found to be associated with neuroblastomas in patients younger than 5 years, whereas in patients above 30 years, it is associated with small round cell tumors (e.g., small-cell carcinoma) and large-cell lymphoma [1]. Ewing's sarcoma is most likely to occur in younger individuals and most commonly in males [11].

Ewing's sarcoma is characterized by small round cell bone tumor and involves pain at the site of tumor and soft tissue swelling around it [1]. Unlike other primary tumors of the bone, Ewing's sarcoma is associated with a characteristic translocation in the 11th and 22nd chromosomes. This translocation results in production of an aberrant transcription factor EWS/FLI1 that forms a complex with RNA helicase A and drives the pathogenesis of Ewing's sarcoma [7, 11]. Its metastasis involves certain non-specific signs of inflammation, anorexia, fever, malaise, fatigue, and weight loss [1].
