History

A 43-year old man had a 2-cm soft tissue mass in the left lower leg that had doubled in size over the previous year. It was painless, hard, firm and deeply attached. Radiography (Fig. 1), computed tomography (Fig. 2) and gadolinium-enhanced magnetic resonance imaging (Fig. 3) were performed. Histopathology is also shown (Fig. 4). What is the diagnosis?

Fig. 1
figure 1

Anteroposterior view of the tibia and fibula

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Fig. 2
figure 2

Computed tomography. Sagittal reconstruction

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Fig. 3
figure 3

Axial planes. a Computed tomography. MRI: 3D T1-weighted sequence with fat saturation, b pre- and c post-administration of intravenous gadolinium

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Fig. 4
figure 4

Hematoxylin and eosin, ×2

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