PMC4899576_01
28-year-old female with left-knee pain. A. Frontal radiograph demonstrated a permeative lytic lesion in the distal femur with wide zone of transition. No osseous matrix was identified. B. Lateral radiograph of the distal femoral permeative lytic lesion demonstrated anterior cortical breakthrough and associated small soft-tissue mass encroaching on the prefemoral fat pad
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The radiographs demonstrated a poorly defined lytic lesion arising from the distal left femur with a wide zone of transition, cortical destruction, and a small anterior soft-tissue component (Fig. 1). 
A. 28-year-old female with left-knee pain. Sagittal T2 fat-saturated MR image (TR = 5600, TE = 55) demonstrated heterogeneously hyperintense intramedullary mass with cortical breakthrough and anterior soft-tissue mass. B. Sagittal T1 precontrast MR image (TR = 750, TE = 10) demonstrated T1 hypointense mass replacing the distal femoral marrow. C. Sagittal T1 fat-saturated postcontrast MR image (TR = 786, TE = 11) demonstrated heterogeneously enhancing intramedullary mass with anterior extracortical extension and small soft-tissue mass.
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This demonstrated a heterogeneously enhancing intramedullary mass within the distal metaphysis of the left femur (Figure 2, Figure 3).
A. 28-year-old female with left-knee pain. Axial T2 fat-saturated MR image (TR = 5600, TE = 55) demonstrated heterogeneously hyperintense intramedullary mass with anterior cortical breakthrough and small soft-tissue mass. B. Axial T1 precontrast MR image (TR = 750, TE = 10) demonstrated T1 hypointense mass replacing the femoral marrow with anterior cortical breakthrough and small soft-tissue mass. C. Axial T1 fat-saturated postcontrast MR image (TR = 786, TE = 11) demonstrated a heterogeneously enhancing intramedullary mass with anterior extracortical breakthrough and small soft-tissue mass.
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This demonstrated a heterogeneously enhancing intramedullary mass within the distal metaphysis of the left femur (Figure 2, Figure 3).
28-year-old female with left-knee pain. A. Sagittal computed tomography image demonstrated a lytic intramedullary lesion of the distal left femur with an anterior cortical breach. B. Sagittal positron emission tomography-computed tomography image demonstrated copious fluorodeoxyglucose avidity within the lytic intramedullary lesion of the distal left femur (maximum standardized uptake value measured 10.1).
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28-year-old female with left-knee pain. MDP bone scan demonstrated intense radiotracer deposition within the distal femur. No lesions suspicious for metastasis were present. Mild tracer deposition of the right ankle and foot was likely inflammatory.
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Figure 5). Findings were most consistent with an osteosarcoma.
A. 28-year-old-female with left-knee pain. Gross pathologic photograph of the distal femur mass with extracortical extension. B. Hematoxylin- and eosin-stain micrograph demonstrated fascicles of highly mitotic spindle cells. C. Smooth-muscle-actin, immunohistochemical-receptor-labeled micrograph demonstrated positive staining for smooth-muscle receptors.
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At resection, the pathology demonstrated well-differentiated leiomyosarcoma that involved the medullary cavity, with focal extension through the cortex into the surrounding soft tissue (Fig. 6A). Histologically, the mass contained fascicles of highly mitotic spindle cells that stained positive for smooth-muscle actin immunohistochemical receptor, also consistent with a well-differentiated leiomyosarcoma (Fig. 6C).