case_images: PMC5867559_01
case_images: Anteroposterior radiographs of the left shoulder (a) 8 years before the presentation and (b) at presentation, showing that the tumor had apparently increased. (c) Axial computed tomography (CT) view of the left shoulder shows the tumor attached to the coracoid process. 3D reconstruction of the left shoulder illustrates structures in (d).
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case_images: fig1
case_images: Plain radiographs of the left shoulder showed that the bony mass adjacent to the clavicle had markedly increased compared with 8 years previously (Figures 1(a) and 1(b)). Computed tomography of the left shoulder showed a bony lesion involving the left clavicle protruding in the posteroinferior direction, adhering to the coracoid process of the scapula; the subclavian artery was located under the tumor (Figures 1(c) and 1(d)).
case_images: (a) T1-weighted magnetic resonance image (MRI). (b) T2-weighted MRI of fat suppression. (c) Contrast-enhanced T1-weighted preoperative MRI of fat suppression, axial view, showing a well-demarcated osseous lesion in the retroclavicular space with a thickened cartilaginous cap at the periphery of the tumor.
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case_images: fig2
case_images: Magnetic resonance imaging (MRI) of the left shoulder revealed a maximal cartilaginous cap thickness of 1.7 cm, and T2-weighted and slightly gadolinium-enhanced MRI showed a high signal intensity of the cartilaginous cap (Figure 2).
case_images: Angiography of the subclavian artery. (a) At the neutral position. (b) At 60  elevation of the left arm, the obstruction of the subclavian artery is released.
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case_images: fig3
case_images: Angiography showed that elevating the left arm dissolved the disruption of the subclavian artery (Figure 3).
case_images: (a) Resection line of the coracoid process. (b) Resection line of the clavicle. (c) Intraoperative findings show that the subclavian artery and brachial plexus are compressed by the tumor. (d) Resected specimen. (e) Postoperative axial computed tomography view shows that the coracoid process is resected and the glenohumeral joint is preserved. (f) Anteroposterior view of the left shoulder 3 years after surgery shows that the tumor is resected from the clavicle and there is no recurrence.
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case_images: fig4
case_images: The clavicle was resected almost in entirety, and the coracoid process was resected from the scapula at its base (Figures 4(a)-4(d)). Neither local recurrence nor metastases were observed 3 years later (Figure 4(f)), and there was no functional disability of the left shoulder and arm.
case_images: Histology of the resected tumor with hematoxylin and eosin stain. (a) On low-power view, the tumor has three layers: superficial perichondrium, thickened cartilage cap with lobular architecture, and endochondral ossification in the base. (b) On higher magnification (square area in (a)), increased cellularity and mild nuclear atypia of the neoplastic chondrocytes are noted.
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case_images: PMC5867559_01_CRIOR2018-9347145.005.jpg
case_images: fig5
case_images: On histological examination, the tumor was determined to be composed of cartilaginous tissue with mild nuclear atypia and increased cellularity showing a lobular growth pattern separated by fibrous bands (Figure 5).