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case_images: Ultrasound of the left upper thigh demonstrating a hypoechoic mass measuring 3.5 x 3 x 2.4 cm.
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case_images: Based on the anatomical location, the ultrasound findings were suspicious for lymphadenopathy (Figure 1) and further evaluation with a CT or biopsy was recommended.
case_images: Histological examination showed haphazardly arranged spindle to stellate cells arranged in a myxoid matrix with mucin pools. FISH analysis revealed the presence of a USP6 rearrangement.
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case_images: One week after the initial ultrasound, an ultrasound-guided biopsy was performed (Figure 2) which showed irregularly arranged bland spindle cells with myxoid stroma.
case_images: MRI demonstrating soft tissue mass measuring 4.8 x 2.7 x 4.0 cm extending into the left gracilis muscle.
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case_images: MRI was performed one month following CT. MRI revealed a mass measuring 4.8 x 2.7 x 4.0 cm extending from the uppermost portion of the left gracilis muscle to the inferior left pubic ramus, which resulted in mass effect on the gracilis muscle (Figure 3).
case_images: The resection specimen showed similar spindle to stellate cells, and also showed irregular fragments of osteoid, consistent with ossifying fasciitis.
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case_images: Histological analysis (Figure 4) revealed short intersecting fascicles of cytologically uniform myofibroblastic spindle cells having ovoid or tapering nuclei and palely eosinophilic cytoplasm.