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. The disease is Ewing sarcoma (MONDO_0012817). Also known as: ES, Ewing's family localised tumour, Ewing's family localized tumor, Ewing's sarcoma, Ewing's tumor, Ewing's tumour, Ewings sarcoma, PNET of Thoracopulmonary region.