case_images: PMC7708320_01
case_images: CT showed a lesion of bone destruction in the right distal fibula. Sagittal (A) and axial (B) CT of bony window showed a centrally osteolytic lesion with an expansive growth pattern, scattered punctate bony sclerosis inside and a local, slight periosteal reaction. Axial CT of soft tissue window images demonstrate a well-demarcated soft tissue mass displayed uneven density in unenhanced phase (C, CT value = 93 HU) and mild enhancement in the arterial phase (D, CT value = 113 HU) and moderate heterogeneous enhancement in the portal phase (E, CT value = 123 HU).
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case_images: Computed tomography (CT) images of bony window showed centrally expansile osteolytic changes with scattered punctate bony sclerosis inside ( Figures 1A, B ). Axial CT images demonstrated a soft tissue mass with heterogeneous density ( Figure 1C ) and mild enhancement in the arterial phase ( Figure 1D ) and moderate enhancement in the venous phase ( Figure 1E ).
case_images: Axial T1-weighted image without contrast enhancement. (A), T2-weighted image (B) and the arterial phase of T1-weighted image (C). The arterial (D) and the venous (E) phase of coronal T1-weighted images. MRI revealed a focal, hypo- and isointense mixed mass on T1-weighted image (A), and hypo- and hyperintense mixed mass on T2-weighted image (B). There were no signs of necrosis, hemorrhage, or cyst formation within the mass. However, adjacent soft tissue edema and swelling was seen. Gadolinium-enhanced T1-weighted images revealed obvious perilesional enhancement, particularly in the region adjacent to the normal tissue (C-E).
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case_images: T1-weighted images (T1WI) ( Figure 2A ), and hypo- and hyperintense mixed mass on T2-weighted images (T2WI) ( Figure 2B ). There were no signs of necrosis, hemorrhage, or cyst formation within the mass. T1WI revealed obvious perilesional enhancement, particularly in the region adjacent to the normal tissue ( Figures 2C-E ). The MRI report suggested an osseous malignant tumor in the right distal fibula.
case_images: Histological images. (A) The tumor consisted of extensive areas of a densely sclerotic hyaline matrix with fibroblastic epithelioid cells arranged in cords, nests, or sheets inside accompanied by partial calcification (hematoxylin and eosin staining; original magnification: x 4). (B) Cells were arranged in nests or clusters (hematoxylin and eosin staining; original magnification: x 10).
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case_images: Histological staining showed that fibroblastic epithelioid cells were ovoid and arranged in nests, cords, or sheets within a collagen-rich extracellular matrix ( Figure 3 ).
case_images: The timeline of diagnosis and treatment.
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case_images: The timeline of diagnosis and treatment was shown in  Figure 4 .