Etiology:

• There are common mutations between this tumour and the primitive neuroectodermal tumour of bone (PNET)
• All cause myc overexpression
  • t(11;22) – 85% of ES & PNET
  • t(24;12) – 5 – 10%
  • t(7;22) – < 1%

Radiology:

• Irregular lytic bone destruction with ill-defined margins.
• “Onion skin” periosteal reaction

Histology:

• Small round cells – well-delineated nuclear outlines + ill-defined cellular borders
• Areas of necrosis and hemorrhage

Diagnosis: 75% of tumors have glycogen in the cytoplasm, so they are PAS positive

Management:

• Combined surgery + Radiotherapy + Multidrug chemotherapy

Picture