PMC7398243_01
Radiologic characterization of endolymphatic sac tumor. a, b CT in the axial plane demonstrated an expansile lytic lesion of left mastoid process and middle ear extending posteriorly to the posterior cranial fossa (a) with apparent enhancement in contrast imaging (b). c-e MR in the axial plane showed the lesion to be uniformity hypo-signal on the T1-weighted (c) and high-low mixed signs on the T2-weighted (d), and obviously enhanced with contrast (e). f Three-dimensional computerized tomographic angiography ( 3D-CTA ) manifested main blood supply of lesion was from the external carotid artery and branches of the subclavian artery
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Fig1
Cerebral computed tomography (CT) findings revealed a bulky enhancing soft tissue mass (maximum transverse diameter was 7.2 cm x 4.6 cm) of left-sided posterior cranial fossa and temporo-occipital region tha t had eroded the skull base bone of middle and posterior cranial fossa (Fig. 1a, b). Cerebral and cervical CT angiography (CTA) revealed the lesion was hypervascular, which main blood supply was from external carotid artery and branches of the subclavian artery, and shadowed of draining veins were visible around the mass, simultaneously (Fig. 1f). Magnetic resonance imaging (MRI) revealed a patchy, massive lesion with irregular, heterogeneous, and lobulated in the left posterior cranial fossa and temporo-occipital region which was showed hypointensity on T1 images (Fig. 1c) and mixed signal intensity on T2-weighted images (Fig. 1d). When given contrast, the lesion obviously showed heterogenous enhancement (Fig. 1e). 
Histopathologic examination of ELST. a Histologic sections revealed a papillary architecture and scattered follicular structures (Hematoxylin-eosin, x 100). b The papillary structures were lined by a single layer offlattenedcuboidal-to-columnar cells. There were mild cellular pleomorphism and rare mitotic activity (Hematoxylin-eosin, x 400)
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Fig2
Postoperative pathology analysis revealed that the tumor cells mainly showed papillary arrangements (Fig. 2a). At high power microscopic view, the papillary structures were found lined by simple cuboidal to columnar epithelioid cells (Fig. 2b).
Immunohistochemical staining of ELST. The tumor cells showed positive reactivity with cytokeratin (Pan) (a), cytokeratin 7 (b), SOX10 (c), and vimentin (d). Positive reactivity of thyroglobulin (e) and S-100 (f) was not observed
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Fig3
The results of immunohistochemical examination revealed diffusely positive reactivity with cytokeratin (Pan) (Fig. 3a), cytokeratin 7 (Fig. 3b), SOX10 (Fig. 3c), vimentin (Fig. 3d), 5-lipoxygenase, Oligo-2, and also showed tiny positive reactivity with GFAP. The immunoreactivity of thyroglobulin (Fig. 3e) and S-100 (Fig. 3f) was negative.