Pediatric Ewing Sarcoma

  • Etiology:
    — Malignant small round blue cell tumor
    — Family of tumors – Ewing sarcoma of bone and extraskeletal Ewing sarcoma and peripheral primitive neuroectodermal tumor and Askin tumor of rib
  • Imaging:
    — Location: Diametaphyseal or diaphyseal, intramedullary, most common sites are axial skeleton (54%) and appendicular skeleton (42%), occurs in both long and flat bones
    — Lytic or blastic:
    — Matrix: (chondroid, osteoid, fibrous)
    — Zone of transition: Wide and poorly marginated
    — Periosteal new bone or cortical destruction: Lamellated or sunburst periosteal reaction and permeative or lytic-sclerotic or sclerotic cortical destruction
    — Additionally: May or may not have associated soft tissue mass
  • Imaging MRI: Look for skip metastases in bone
    — T1WI: Heterogenous and hypointense
    — T1WI post contrast: Heterogenous enhancement
    — T2WI: Heterogenous and hyperintense
  • DDX: Osteomyelitis, osteosarcoma
    — Can mimic osteomyelitis and be associated with leukocytosis, fever, increased sedimentation rate
    — Periosteal reaction is sunburst in osteosarcoma versus onion skin in Ewing sarcoma
    — Tumor margins on MRI are sharp in osteosarcoma versus infiltrative in Ewing sarcoma
    — Focal bone metastases in osteosarcoma versus bone marrow involvement in Ewing sarcoma
  • Complications:
    — 25% have metastases at diagnosis to lung or bone or bone marrow or skip metastasis to bone
    — Almost always micrometastatic at diagnosis
    — Presence of overt metastatic disease at diagnosis is strongest adverse clinical prognostic indicator
  • Treatment: Chemotherapy then surgical
  • Clinical:
    — Occurs in 10-20 years old
    — Second most common primary bone tumor and soft tissue tumor in childre
    — Most common tumor of pelvic bones in children

Askin Tumor

  • Etiology: Ewing sarcoma arising from rib
  • Imaging:
    — Large intra and extrathoracic mass
    — Heterogenous due to necrosis and hemorrhage
    — Rarely calcified
    — Rib destruction
    — Pleural thickening and effusions
  • DDX:
  • Complications:
  • Treatment: Chemotherapy then surgical
  • Clinical:
    — Most common malignant chest wall mass in children
    — Most common rib malignancy in children

Ewing Sarcoma of Spine

  • Etiology: Ewing sarcoma arising from spine
    — Imaging: Mimics other vertebral body tumors with vertebral body collapse and intradural and extradural spinal extension
  • Imaging CT: Ivory vertebra
  • DDX: Langerhans cell histiocytosis – Ewing sarcoma of spine has more soft tissue involvement than Langerhans cell histiocytosis which is usually seen in younger children
  • Complications: Metastasis in 30% at presentation
  • Treatment: Chemotherapy then surgical
  • Clinical:
    — Most common primary malignancy of spine in children
    — 90% present by age 20

Radiology Cases of Ewing Sarcoma

Radiology Cases of Ewing Sarcoma of the Extremities

Radiograph of Ewing Sarcoma
AP radiograph of the right hip shows a permeative appearance to the medullary portion of the proximal femur with cortical destruction and diffuse periosteal reaction.

Radiology Cases of Ewing Sarcoma of the Rib / Askin Tumor

CT of Ewing sarcoma of the rib
Axial CT with contrast of the chest shows a large heterogenous non-enhancing soft tissue mass centered around the posterior aspect of the right 11th rib. 3D CT reconstruction better demonstrates the lesion’s origin from the right 11th rib.
CXR and CT of Ewing Sarcoma of the rib / Askin Tumor
CXR AP and lateral (above) show a large right sided chest mass whose obtuse angles with the chest wall suggest it is extrapleural in origin. Axial CT without contrast of the chest (below) shows the mass to be arising from a rib and to be causing periosteal reaction.
CXR and CT of Ewing sarcoma of the rib / Askin tumor
CXR PA and lateral (above) show a round mass on the lateral and middle aspect of the dome of the left hemidiaphragm. Axial CT with contrast of the chest (below) shows the soft tissue mass to be arising from a rib which has extensive and aggressive periosteal reaction.

Radiology Cases of Ewing Sarcoma of the Spine

Radiograph and CT of Ewing sarcoma of the spine
Lateral radiograph of the spine shows collapse of the T12 vertebral body. Sagittal 2D reconstruction and axial CT without contrast of the T12 vertebral body in bone windows shows a permeative destructive process affecting it. Axial CT without contrast of the abdomen at the T12 level shows a large left-sided paraspinal soft tissue mass.

Gross Pathology Cases of Ewing Sarcoma

Pathology image of Ewing sarcoma of the rib
Gross pathological image after a chest wall and diaphragm resection shows the left seventh rib and part of the eighth rib with the tumor adherent to their inner surface. A portion of shiny white pleura is attached to the tumor and portions of lung are seen above and to the left of the tumor.
Pathological image of Ewing sarcoma of the rib
Pathological image shows a tumor which was brown and grossly necrotic and was seen to be located predominantly in the soft tissues and not in the rib.

Histopathology Cases of Ewing Sarcoma

Histopathology image of Ewing sarcoma
Histopathological image of H&E stained section shows sheets of undifferentiated small round blue cells.