PMC3114461_01
MRI with (a) axial T1 (TR 602, TE 40), (b) axial short tau inversion recovery (STIR; TR 4910, TE 40), and (c) contrast enhanced coronal T1 fat saturated(TR 540, TE 13) sequences showed a heterogeneous soft tissue mass at the insertion of pes anserinus conjoint tendon with peripheral and septal enhancement. The decreased interspersed signal on all images was due to hemosiderin deposits. There was no evidence of bone or joint involvement.
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fig1
The magnetic resonance imaging (MRI) showed a 4.5 x 3.0 x 2.0 cm soft tissue mass at the insertion of pes anserinus conjoint tendon (Figures 1(a)-1(c)).
(a) Intraoperative photograph of the lesion and (b) the gross specimen showed multiple yellow to brown nodules inside the pes anserine bursa (ST: semitendinosus tendon).
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fig2
The specimen consisted of a brownish-yellowish lobulated multinodular mass in the pes anserinus bursa and measured 4.5 x 3.0 x 1.8 cm (Figures 2(a)-2(b)).
(a) Histopathological slide showed villous proliferation covered by reactive appearing synovial cells (H&E, x4). The cores of the villi had a cellular infiltrate consisting of mononuclear cells and foamy histiocytes with scattered giant cells ((b); H&E, x20).
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fig3
Histopathology showed osteoclast-like multinucleated giant cells in a mononuclear background with foci of hemosiderin deposits (Figures 3(a)-3(b)).