Name : Hamidreza
Resident : Payam Asadi
Gender : Female
Age : 9
A 9 Y/O girl with low back pain
Imaging Procedures and Findings
Plain X ray shows lytic lesion in left S1 ala. Axial CT scan reveals lytic-sclerotic lesion in left S1 body and ala. Periosteal reaction is seen at anterior cortex of left ala. Soft tissue component is visible which extends to canal . Saggital T1WI demonstrates exteradural mass with low signal in T1WI arising from posterior of S1 .Areas of S1 body involvement is visible as low signal in T1WI. Posterior cortex of S1 in destructed.
Ewing's sarcoma is a round cell sarcoma of the bone that occurs mostly in children and teenagers. There is a second small age peak in the fifth to sixth decades. The prognosis of Ewing's sarcoma of the spine tends to be worse than that of peripheral Ewing's sarcoma, most likely owing to the more limited options for surgical resection. Ewing's sarcoma tends to affect the center of the vertebral body before spreading to the neural arch. The sacrum is more commonly affected than the remainder of the spine. On plain-film radiography, bone destruction with a wide zone of transition can usually be found. The pattern may be permeative or moth-eaten. The tumor matrix itself does not calcify; in rare instances, sclerotic lesions may be present as a sign of host reaction. Likewise, on CT, the pattern of bone destruction is permeative, with a wide zone of transition. The perforations of the cortical bone are usually comparatively small,and the cortical structures commonly appear relatively intact. MRl is usually the imaging method of choice because it is best at showing the involvement of bone and sof tissue. The affected marrow appears hypointense on T1 weighted sequences and intermediate to hyperintense on T2-weighted sequences compared with unaffected bone marrow . After contrast administration, intermediate enhancement is usually seen. Commonly, areas of necrosis are present.
Haaga John R. , MRI And CT of Whole Body. 5th edition. P814-817