Question

HISTORY: A 46-year-old male had progressive and complete loss of supination of the right wrist, without pain or prior trauma. Normal radiographs and CT arthrography of the wrist were taken. Ultrasonography (Fig. 1) followed by MRI was performed (Fig. 2) as was a US-guided biopsy (Fig. 3).

Fig. 1
figure 1

Longitudinal slice of the anterior side of the right wrist (a) with Doppler (b).

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Fig. 2
figure 2

T1-weighted MRI (a). Fat-suppressed proton density-weighted MRI (b). Fat-suppressed T1-weighted MRI after gadolinium chelate injection (c, d)

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Fig. 3
figure 3

Hematoxylin-eosin saffron staining (magnification ×100) (a). Immunohistostains including S100-protein (b) and CD-68 (c)

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