PMC6630396_01
Magnetic resonance imaging presentation of the tumor: The enhanced mass on axial view (proton density fat saturated image, turbo spin echo sequence) (A) and magnetic resonance imaging presentation of the tumor: Signs of dysplasia in the patellofemoral joint on sagittal view (T1-weighted image, turbo spin echo sequence) (B)
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A post-traumatic inflammatory lesion of the medial patellar retinaculum of the left knee was suggested (Fig. 1).
The hematoxylin and eosin microscopic images show a non-capsulated, well-circumscribed tumor with heterogeneous structure - elements of fibrous connective tissue, hyalinization, cartilage, bone and osteoid formation visible. Magnification of 20x (A), 100x (B), 40x (C), 400x (D)
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In the macroscopic examination (Fig. 2), the surgical specimen was 5 cm x 4 cm x 2 cm in size and it was of fibrous, fatty structure.
Immunophenotype of the tumor: positivity for smooth muscle actin (A), negativity for S-100 protein (B), partial positivity for Myo-D1 (C), proliferation index of Ki-67 up to 5% (D). Magnification of 100x
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An immunohistochemical analysis (Fig. 3) showed positivity for smooth muscle actin (SMA) and a weak partial positivity for MyoD1 and neuron-specific enolase (NSE).