Ewing sarcoma family of tumors (ESFT), also referred as Ewing sarcomas of the chest wall, are malignant tumors affecting children and young adults, originating either from the osseous structures or the soft tissues of the chest wall. On imaging, they are usually characterized as large extrapulmonary invasive soft tissue masses that are heterogeneous due to the presence of hemorrhage, necrosis, or cystic changes.

Small round blue cell tumors are a large number of tumors that share similar histology, composed of relatively uniform primitive small round blue cells. They also share many demographic, radiographic and clinical similarities.

Originally a small round blue cell tumor of the soft tissues of the chest was described and became known as an Askin tumor or peripheral primitive neuroectodermal tumor (pPNET). All three entities are now thought to belong to the same tumor family, now referred to as the Ewing sarcoma family of tumors (ESFT).