PMC9422175_01
Preoperative CT examination of the paranasal sinus. The CT examination showed an inhomogeneous mass in the right sphenoid sinus cavity, and steolytic bone destruction and defect in the parietal wall of sphenoid sinus. (A) Sagittal image and (B) coronal image. (The mass is marked with a black arrow.).
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The computed tomography (CT) scan showed an inhomogeneous mass in the right sphenoid sinus cavity, and steolytic bone destruction and defect in the parietal wall of sphenoid sinus ( Figure 2 ).
Preoperative MR examination of the paranasal sinus. The MR examination detected a solid mass in the right sphenoid sinus that had extended into the right orbital apex and posterior ethmoid sinus. (A) Axial T1-weighted image. (B) Axial T2-weighted image. (C) Axial T1-weighted enhanced image. (D) Sagittal T1-weighted enhanced image. (E) Coronal T1-weighted enhanced image. (The mass is marked with a black arrow.).
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Contrast magnetic resonance imaging (MRI) was then used to determine the extent of the tumor, and displayed a solid mass in the right sphenoid sinus that had extended into the right orbital apex and posterior ethmoid sinus ( Figure 3 ).
Histological and immunohistochemical features of the tumor of sphenoid sinus. (A, B) Hematoxylin and eosin (H & E) staining of a tumor specimen showing small round atypical cells with densely stained chromatin and high nuclear cytoplasmic ratios. (B, C) Immunohistochemical staining of a tumor specimen showing diffuse positive staining for CD99 on the tumor cell membrane. (A, C): Original magnification x 100; B, D: Original magnification x 400.).
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Postoperative histopathological examination showed that the tumor cells were small oval or round with scanty cytoplasm, and round or oval vesicular nuclei ( Figures 4A, B ). Immunohistochemistry revealed membranous positivity for CD99 ( Figures 4C, D ), diffuse nuclear positivity for NKX2.2, diffuse cytoplasmic positivity for vimentin and sporadic positivity for Syn and EMA, strongly suggesting a diagnosis of Ewing's sarcoma.
Postoperative MR examination of the paranasal sinus. The MR examination detected a residuary tumor in the surgical area and the lateral side and the tip of the right orbit. (A) Axial T1-weighted image. (B) Axial T2-weighted image. (C) Axial T1-weighted enhanced image. (D) Sagittal T1-weighted enhanced image. (E) Coronal T1-weighted enhanced image. (The mass is marked with a black arrow.).
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The contrast MRI was conducted to evaluate the tumor status, and a residuary tumor was detected in the surgical area ( Figure 5 ).
Dose planning of radiotherapy. Planned target volume (GTV: red, PGTV: pink, CTV: light blue, and PTV: blue) covered by the 95% isodose can be seen in axial (A), coronal (C), and sagittal (D) planes on pretreatment planning computed tomography. (B) The dose-volume histogram showed that 95% of the PGTV and PTV volumes irradiated with more than 5,040 cGy and 5,600 cGy.
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Then, intensity-modulated radiotherapy [gross target volume (GTV) 5,600 centigray (cGy)/28 fractions, clinical target volume (CTV) 5,040 cGy/28 fractions, with details summarized in  Figure 6 ] and anti-angiogenic therapy (anlotinib, 10 mg on days 1-14, every 3 weeks) were conducted on the basis of chemotherapy.
Postradiotherapy MR examination of the paranasal sinus. The MR examination detected a complete remission of the tumor. (A) Axial T1-weighted image. (B) Axial T2-weighted image. (C) Axial T1-weighted enhanced image. (D) Sagittal T1-weighted enhanced image. (E) Coronal T1-weighted enhanced image.
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After 4 weeks of radiotherapy, there was a complete remission of the tumor by the RECIST criteria ( Figure 7 ).