case_images: PMC7548957_01
case_images: Plain radiograph: Anteroposterior views show soft tissue mass in plantar and heel of right foot (A), lateral view shows subcutaneous soft tissue mass in foot plantar and heel with slight calcaneus periosteal irregularity of calcaneus bone (B).
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case_images: The plain radiography of foot showed a large subcutaneous soft tissue mass in plantar area and heel, possibly with peripheral chunky calcification (Fig. 1).
case_images: T1- and T2-weighted MRI in sagittal (A, B) and axial (c) planes demonstrating a large soft tissue mass superficial to the deep plantar fascial plane and embedded within the subcutaneous and deep dermis tissue. The lesion has a low signal intensity on T1weighted images (A) and heterogeneous signal intensity on T2-weighted images (B, C).
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case_images: T1-weighted images and hyperintense signal intensity on T2 (Fig. 2). The lesion did not invade subjacent bone or muscle but extended into subcutaneous areas and providing extensive subcutis edema.
case_images: Microscopic appearance of subcutaneous soft tissue tumor shows osteoid formation surrounded by malignant osteoblastic cells without interposition of cartilage (A, B) (HE, x100), (C) (HE, x200), neoplastic cells with marked atypia (pleomorphic, hyperchromatic) and bizarre giant tumor cells noted (D) (HE, x200). Immunohistochemistry staining: cytoplasmic positive immunoreactivity of CD99 in tumoral cells of osteosarcoma (IHC x200) (E), cytoplasmic positive immunoreactivity of osteocalcin in tumoral cells of osteosarcoma (IHC x200) (F).
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case_images: The stain for the Ki-67 analogous MIB-1 shows high proliferative activity with values around 30% (Fig. 3).
case_images: Intraoperative macroscopic appearance of subcutaneous soft tissue tumor indicates tumor was marginally resected and preserved the major neuro-vascular bundles, tendons and muscles (A, B).
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case_images: The connective tissue capsule surrounded the tumor and adhered to the subjacent structures that made surgical dissection difficult (Fig. 4).