Ewing Sarcoma

**Semantic type:** Neoplastic Process

**Definition:** A small round cell tumor that lacks morphologic, immunohistochemical, and electron microscopic evidence of neuroectodermal differentiation. It represents one of the two ends of the spectrum called Ewing sarcoma/peripheral neuroectodermal tumor. It affects mostly males under age 20, and it can occur in soft tissue or bone. Pain and the presence of a mass are the most common clinical symptoms.

**Synonyms:** - ES - Ewing sarcoma - Ewing sarcoma - Ewing tumor - Ewing's Sarcoma - Ewing's Tumor