CASE 141

By: Dr. Nizar Al-Nakshabandi MD, FRCPC

HISTORY: 10-year-old boy complaining of left leg pain and swelling.

What are your findings?

What is the differential diagnosis?

What are the causes?

FINDINGS:

The AP radiograph of the left tibia and fibula [A] and lateral view [B] demonstrate an ill defined lytic lesion permeative lesion with laminated periosteal reaction.

Coronal T1 weighted image through the left tibia demonstrate complete replacement of the yellow marrow with a soft tissue mass that has extended outside the confines of the tibia into the leg muscles medially, laterally and posteriorly. The lesion stops at the physeal plate.

Axial T1 weighted fat suppressed image with IV gadolinium demonstrates avid enhancement of the periphery of the lesion with central necrosis. Furthermore, there is no involvement of the neurovascular bundle. The joint space is spared and there is no evidence of adjacent lymphadenopathy.

DIFFERENTIAL DIAGNOSIS:

·        Ewing’s sarcoma.

·        Osteosarcoma.

·        Osteomyelitis.

·        Hematological malignancy.

·        Metastasis.

DIAGNOSIS:

Ewing’s sarcoma of the tibia.

PEARLS AND DISCUSSION:

Ewing sarcoma, a highly malignant primary bone tumor that is derived from red bone marrow, was first described by James Ewing in 1921. 

The radiographic appearance of Ewing sarcoma may mimic that of osteomyelitis, as well as those of other malignant tumors, such as leukemia. The appearance of Ewing sarcoma may vary from that of pure lysis to sclerosis. MRI findings alone may not be conclusive for a malignant lesion, but MRI help to show the full extent of tumor spread and extension. The use of gadolinium-based contrast agents does not add significant value to the MRI evaluation of Ewing sarcoma. On T1-weighted images, the tumor has low signal with heterogeneous gadolinium enhancement, whereas signal intensity on T2-weighted images varies after contrast enhancement.

CT scanning helps to define the bone destruction that is associated with Ewing sarcoma. Tumor size can be evaluated with contrast-enhanced CT scanning, which may be used in follow-up evaluation during chemotherapy.

FURTHER READING:

1.      Murphey MD, Andrews CL, Flemming DJ et-al. From the archives of the AFIP. Primary tumors of the spine: radiologic pathologic correlation. Radiographics. 1996;16 (5): 1131-58. Radiographics 

2.      Meyers SP. MRI of bone and soft tissue tumors and tumorlike lesions, differential diagnosis and atlas. Thieme Publishing Group. (2008) 

3.      Weissleder R, Wittenberg J, Harisinghani MG. Primer of diagnostic imaging. Mosby Inc. (2003)  ISBN:0323023282.