Clinical information
A 52-year-old man presented with an 8-month history of progressive pain and swelling of his right upper arm. His past medical history was unremarkable.
Physical examination showed a soft doughy mass around the right shoulder, but no heat or redness was noted. Shoulder range of motion was significantly limited. The patient was free of systemic symptoms. Laboratory evaluation was within normal limits.
Radiographs demonstrated two lucent defects in the head of the right humerus and a soft tissue mass without any calcification (Fig. 1). Magnetic resonance (MR) imaging of the shoulder including axial and coronal planes revealed a lobulated mass in the subcapsular bursa, the axillary and posterior recesses, and around the long head of the biceps.
On spin echo (SE) Tl-weighted images, the signal of the mass was slightly higher than that of the surrounding muscle and showed a homogeneous enhancement after gadolinium injection (Figs. 2,3). Small low-signal areas were seen inside the mass around the bicipital tendon before contrast injection; they did not enhance.
On SE T2-weighted images, the mass had a slightly hyperintense signal compared with the muscles and