HISTORY: A 34 year-old man presented to his primary care physician with a painless mass along the dorsum of the second metacarpal neck of 8–9 months duration. There was no history of trauma. (Figs. 1, 2 and 3)

Fig. 1
figure 1

AP radiograph of the right 2nd-4th metacarpals and proximal phalanges

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Fig. 2
figure 2

Axial (a), coronal (b), and sagittal (c) noncontrast CT of the right hand at bone windows

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Fig. 3
figure 3

Histopathological photomicrographs (hematoxylin and eosin staining) at (a) 40x power and (b) 100x power

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