PMC3350087_01
Frontal (a) and lateral (b) radiographs of the distal right femur. The lesion is shown as an expansile, fusiform mass in the distal femur, away from the growth plate. Medullary involvement is shown as patchy, moth-eaten lucencies. Smooth laminated onion-skin like periosteal reaction is also seen.
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fig1
Radiographs of the femur and knee (Figure 1) revealed an expansile, moth-eaten appearing bony lesion with poorly defined margins centered in the distal diaphysis of the femur.
Axial 1.25 mm image enhanced CT through the lesion. The right femoral lesion is well shown on CT, including cortical thickening, cortical lucencies (thin white arrow), and periosteal reaction (black arrows). Note the size discrepancy between the right and left femurs in keeping with the clinically seen asymmetry and fusiform swelling.
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fig2
CT of the distal femur following IV contrast (Figure 2) revealed similar findings to the radiographs.
Frontal projection femoral blood pool (a) and 2-hour delayed whole-body (b) images from 99 mTc MDP bone scan. Intense activity is present at the right distal femoral lesion. There were no other active sites, confirming this to be a solitary lesion.
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fig3
A technetium bone scan (Figure 3) showed the lesion to have intense activity on both blood pool and delayed static views.
Axial (a-b) MRI through the right thigh with coronal (c-d) MRI images through both thighs. Displayed axial images are from the level of the white lines in (c) and (d). Sequences are as follows: (a) axial T2 fat saturated (FS) (TE 93 ms. TR 5670 ms.), (b) axial T1FS with gadolinium (TE 17 ms. TE 730 ms.), (c) coronal T1 (TE 14 ms. TR 543 ms.), and (d) coronal T1FS with gadolinium (TE 14 ms. TR 460 ms.). The axial T2 FS image displays the edematous high signal in the medullary space, patchy high signal cortical lesions (black arrows), cortical thickening and periosteal reaction (thick grey arrows), and subtle surrounding soft tissue edema (thin grey arrows). Coronal T1 (c) shows the low signal within the medullary space, a characteristic feature of involvement. After gadolinium (b,d) there is intense enhancement of the marrow, periosteum (thick grey arrows), with some enhancement also seen in the bordering musculature (thin grey arrows).
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fig4
MRI (Figure 4) again showed the mass to be expansile, centered within the distal diaphysis with periosteal reaction.