Extraskeletal Ewing Sarcoma/Peripheral Primitive Neuroectodermal Tumor

**Semantic type:** Neoplastic Process

**Definition:** A spectrum of malignant tumors arising from the soft tissues, characterized morphologically by the presence of small round cells. Ewing sarcoma and peripheral primitive neuroectodermal tumor represent the ends of a spectrum, with Ewing sarcoma lacking evidence of neural differentiation and the markers that characterize the peripheral primitive neuroectodermal tumor. Ewing sarcoma and peripheral primitive neuroectodermal tumor may share cytogenetic abnormalities, proto-oncogene expression, cell culture and immunohistochemical abnormalities. Pain and the presence of a mass are the most common clinical symptoms.

**Synonyms:** - Extraosseous Ewing Sarcoma/Peripheral Primitive Neuroectodermal Tumor - Extraosseous Ewing Sarcoma/Peripheral Primitive Neuroectodermal Tumor - Extraosseous Ewing's Sarcoma/Peripheral Primitive Neuroectodermal Tumor