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Neuroradiology Case of the Week
Case 310
Adam J. Weller, MSIV
Clinical
Presentation: Patient is a 12-year-old female with headache, left-sided numbness, and a known parafalcine mass.
Imaging Findings: MRI of the head shows a large well-defined extra-axial lesion in the right parafalcine region. The lesion demonstrates low-signal on T1 that enhances strongly with contrast and heterogeneously increased signal on T2. The lesion is seen to extend out both sides of the parietal bone with mass effect and edema noted intercranially and extracranial involvement of the subcutaneous soft tissues at the vertex.
CT scan of the pelvis shows a bony lesion involving the left iliac bone. The bone appears heterogeneous and sclerotic and a large soft tissue mass can be seen extending from the bone laterally and extending inferiorly into the obturator region. Also found were lung nodules and subtle lesions in the L-spine (not shown).
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Figure 1: Coronal SPGR with contrast. The metastatic lesion can be visualized here as a well circumscribed, enhancing mass to the right of midline. The scalp component is also visualized. |
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Figure 2: Axial T1-weighted MR. A) On axial T1 pre-gadolinium image a mass can be seen with low to intermediate signal intensity in the right post-parietal parafalcine area. B) Axial T2 post-gadolinium image shows a well-circumscribed heterogeneously enhancing lesion. |
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Figure 3: Axial T2-weighted MR. Lesion is seen as a well-circumscribed mass with heterogeneous signal. Increased signal in surrounding brain parenchyma is localized edema. |
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| Figure 4: CT scan of the pelvis. A) Bony window shows what is presumed to be the primary lesion. The left iliac bone is sclerotic with slight expansion, cortical breakthrough, and periosteal reaction. B) Soft tissue window shows two soft tissue masses extending out from the bone, these continue inferiorly into the obturator space. |
Diagnosis: Metastatic Ewing's sarcoma
Discussion: Ewing’s sarcoma is a primary bone tumor that is known to be highly malignant and accounts for 10% of all bone tumors. While the exact cell line of origin is unknown, it is thought to be derived from neural crest cells in bone marrow, and has been associated with a t(11;22) translocation. Typically, Ewing’s sarcoma develops in children and adolescents between the ages of 4 and 15, and rarely in those above age 30.
While Ewing’s sarcoma may involve any bone, normally the lesion is initially discovered as a monostotic lesion varying from sclerotic to lytic in the metaphysis or diaphysis of the long bones. The clinical presentation usually consists of pain and localized swelling which is intermittent at the onset, but can eventually become quite intense. Frequently, the diseased area can show local redness and swelling with hyperthermia. Also, nerve root symptoms and cord compression can be present if the axial spine is involved.
The preferred imaging for diagnosis and staging of Ewing’s sarcoma is MR. On T1-weighted imaging the tumor will have a low signal with heterogeneous gadolinium enhancement. On T2-weighted imaging the lesions are typically hyperintense compared to surround soft tissue. Normally, the tumor can be seen on plain radiograph as lytic lesion in the metaphysic and diaphysis of the bone and a prominent soft tissue mass extending from the bone is often associated. Sclerotic lesions such as the pelvic lesion in this case are much less common. Periosteal reaction is typically present with onion-skinning and sunburst seen in more aggressive tumors.
Ewing’s is known to disseminate widely primarily by the hematogenous route, with 20-30% of patients having evidence of metastasis at diagnosis. Typical sites of metastasis are the lungs (38%), bone (31%), and bone marrow (11%). The percentage of Ewing's sarcoma that metastasizes to the brain is unknown, and a wide range has been reported (2.2% - 33%). As the typical route of metastases is via the blood, CNS involvement is thought to be due to hematogenous spread to the skull with subsequent direct extension of the sarcoma to the extradural space and meninges.
The prognosis for the treatment of Ewing's sarcoma is low. If metastasis is present at diagnosis the 5 year survival is only 25%, if no metastasis are present this increases to 50%. Treatment is multimodal, combining surgery, radiation, and chemotherapy.
References:
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Strauss LG. Ewing sarcoma. Emedicine, Nov 2, 2007. http://www.emedicine.com/radio/topic275.htm
- Toretsky JA. Ewing sarcoma and primitive neuroectodermal tumors.
Emedicine, Apr 20, 2007. http://www.emedicine.com/ped/topic2589.htm
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Hattori T, Yamakawa H, Nakayama N, Kuroda T, Andoh T, Sakai N, Ohno T, Nishimoto Y, Takeuchi S, Shimizu K. Skull metastasis of Ewing's sarcoma--three case reports. Neurol Med Chir (Tokyo). 1999 Dec;39(13):946-9. [Medline]
- Mizushima H, Jinbo H, Shimazu M, Abe T, Kunii N, Matsumoto K. Central nervous system metastases from Ewing's sarcoma--case report. Neurol Med Chir (Tokyo). 1994 Nov;34(11):754-8. [Medline]
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Riggi N, Stamenkovic I. The Biology of Ewing sarcoma. Cancer Lett. 2007 Aug 28;254(1):1-10. [Medline]
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