case_images: PMC6591654_01
case_images: STIR FSE coronal MRI showing a soft tissue tumor in the proximal third of the
  right leg with fusiform morphology. FSE indicates fast spin echo; STIR,
  Short-TI Inversion Recovery; MRI, magnetic resonance imaging.
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case_images: On magnetic resonance imaging (MRI), malignant features were detected, with a vast infiltrative component of the adjacent neurovascular structures, suggestive of sarcoma of undetermined characteristics (Figure 1).
case_images: Foot dorsiflexion motion after resection and tendinous transfer surgery.
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case_images: Surgical removal of the lesion was accomplished in March 2017 through an anterior approach, resecting the muscles from the aforementioned compartment, and with immediate reconstruction with a tendinous transfer of the tibialis posterior muscle, so the patient would be able to retain foot dorsiflexion (Figure 2).
case_images: Macroscopic image corresponding to the bloc, free-border resection of the
  tumor located in the lower limb. Tumor size 13 x 5 x 5 cm3.
  Pearl-colored lesion, with focal yellowish areas, that represents necrosis
  areas and minor read-colored areas that correspond with hemorrhage foci.
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case_images: These areas were not in contact with the surgical margins (Figure 3).
case_images: Hematoxylin-eosin (10x): atypical cellular proliferation of mesenchymal cells
  of epithelioid and fusiform morphology, disposed in a fascicular and
  storiform pattern.
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case_images: Histologically, the mass showed a hypercellular atypical proliferation of mesenchymal cells, disposed in a fascicular and storiform pattern and displayed an epithelioid morphology with zones of fusocellular morphology (Figure 4).
case_images: Immunohistochemistry: caldesmon, actin, calponin, and desmin diffuse
  positive, which confirms smooth muscle origin and the diagnosis of
  leiomyosarcoma. Nuclear positivity to estrogen receptor suggests a
  metastatic gynecological origin; in this case, a STUMP. STUMP indicates
  smooth uterine muscle tumors of uncertain malignant potential.
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case_images: Immunohistochemistry was positive for vimentin, cytokeratin AE1-AE3, desmin, calponin, caldesmon and weak for estrogens receptors (Figure 5).